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Paul Wells | 2 Oct 2009 19:10
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Re: SR 612546021 - SNMP responses for the "ospfNbrTable" mib variable

[followups to cs-ospf]

Hi Joe,

Responses inline:

Anirban Karmakar (akarmaka) wrote:
> Adding ospf mailer list
> 
>  
> 
> *From:* Joe Reekers (jreekers)
> *Sent:* Friday, October 02, 2009 9:01 PM
> *To:* cs-snmp (mailer list); cse-tac-snmp(mailer list)
> *Subject:* SR 612546021 - SNMP responses for the "ospfNbrTable" mib variable
> 
>  
> 
> *2nd try - expanding audience*
> 
>  
> 
>  
> 
> 7206VXR IOS 12.3(22)
> 
>  
> 
> Hi Team.
>
(Continue reading)

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Sinbad | 6 Oct 2009 12:20
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ospf backbone area

             ...........................
             .   +                     .
             .   | 3+---+              .      N12      N14
             . N1|--|RT1|\ 1           .        \ N13 /
             .   |  +---+ \            .        8\ |8/8
             .   +         \ ____      .          \|/
             .              /    \   1+---+8    8+---+6
             .             *  N3  *---|RT4|------|RT5|--------+
             .              \____/    +---+      +---+        |
             .    +         /      \   .           |7         |
             .    | 3+---+ /        \  .           |          |
             .  N2|--|RT2|/1        1\ .           |6         |
             .    |  +---+            +---+8    6+---+        |
             .    +                   |RT3|------|RT6|        |
             .                        +---+      +---+        |
             .                      2/ .         Ia|7         |
             .                      /  .           |          |
             .             +---------+ .           |          |
             .Area 1           N4      .           |          |
             ...........................           |          |
          ..........................               |          |
          .            N11         .               |          |
          .        +---------+     .               |          |
          .             |          .               |          |    N12
          .             |3         .             Ib|5         |6 2/
          .           +---+        .             +----+     +---+/
          .           |RT9|        .    .........|RT10|.....|RT7|---N15.
          .           +---+        .    .        +----+     +---+ 9    .
          .             |1         .    .    +  /3    1\      |1       .
          .            _|__        .    .    | /        \   __|_       .
          .           /    \      1+----+2   |/          \ /    \      .
          .          *  N9  *------|RT11|----|            *  N6  *     .
          .           \____/       +----+    |             \____/      .
          .             |          .    .    |                |        .
          .             |1         .    .    +                |1       .
          .  +--+   10+----+       .    .   N8              +---+      .
          .  |H1|-----|RT12|       .    .                   |RT8|      .
          .  +--+SLIP +----+       .    .                   +---+      .
          .             |2         .    .                     |4       .
          .             |          .    .                     |        .
          .        +---------+     .    .                 +--------+   .
          .            N10         .    .                     N7       .
          .                        .    .Area 2                        .
          .Area 3                  .    ................................
          ..........................



1) In the above ospf topology according to ospf rfc 2328 in section 3.4, it states that

   "Note that a failure of the line between Routers RT6 and RT10
   will cause the backbone to become disconnected."

Though there is router RT7 in area 2 still connected to the backbone.It confused my understanding of
disconnected backbone area. Can someone shed some light on this.


2) why should routers connected by a point to point link having interface addresses assigned,
  should advertise a stub link a stub connection to the other router's interface address.


thanks <div> <span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ...........................</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp; +&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp; | 3+---+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; N12&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; N14</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; . N1|--|RT1|\ 1&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; \ N13 /</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp; |&nbsp; +---+ \&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 8\ |8/8</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp; +&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; \ ____&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; \|/</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; /&nbsp;&nbsp;&nbsp; \&nbsp;&nbsp; 1+---+8&nbsp;&nbsp;&nbsp; 8+---+6</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; *&nbsp; N3&nbsp; *---|RT4|------|RT5|--------+</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; \____/&nbsp;&nbsp;&nbsp; +---+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; +---+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp; +&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; /&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; \&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |7&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp; | 3+---+ /&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; \&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp; N2|--|RT2|/1&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 1\ .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |6&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp; |&nbsp; +---+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; +---+8&nbsp;&nbsp;&nbsp; 6+---+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp; +&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |RT3|------|RT6|&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; +---+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; +---+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 2/ .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Ia|7&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; /&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; +---------+ .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .Area 1&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; N4&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ...........................&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ..........................&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; N11&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; +---------+&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |&nbsp;&nbsp;&nbsp; N12</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |3&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Ib|5&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |6 2/</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; +---+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; +----+&nbsp;&nbsp;&nbsp;&nbsp; +---+/</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |RT9|&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp; .........|RT10|.....|RT7|---N15.</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; +---+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; +----+&nbsp;&nbsp;&nbsp;&nbsp; +---+ 9&nbsp;&nbsp;&nbsp; .</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |1&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp; +&nbsp; /3&nbsp;&nbsp;&nbsp; 1\&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |1&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; _|__&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp; | /&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; \&nbsp;&nbsp; __|_&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; /&nbsp;&nbsp;&nbsp; \&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 1+----+2&nbsp;&nbsp; |/&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; \ /&nbsp;&nbsp;&nbsp; \&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; *&nbsp; N9&nbsp; *------|RT11|----|&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; *&nbsp; N6&nbsp; *&nbsp;&nbsp;&nbsp;&nbsp; .</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; \____/&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; +----+&nbsp;&nbsp;&nbsp; |&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; \____/&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp; |&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |1&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp; +&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |1&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp; +--+&nbsp;&nbsp; 10+----+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp; N8&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; +---+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp; |H1|-----|RT12|&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |RT8|&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp; +--+SLIP +----+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; +---+&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |2&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |4&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; |&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; +---------+&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; +--------+&nbsp;&nbsp; .</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; N10&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; N7&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp; .Area 2&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .Area 3&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; .&nbsp;&nbsp;&nbsp; ................................</span><br><span>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ..........................</span><br><br><br><br>1) In the above ospf topology according to ospf rfc 2328 in section 3.4, it states that <br><br>&nbsp;&nbsp; "Note that a failure of the line between Routers RT6 and RT10<br> &nbsp;&nbsp; will cause the backbone to become disconnected."<br><br>Though there is router RT7 in area 2 still connected to the backbone.It confused my understanding of <br>disconnected backbone area. Can someone shed some light on this.<br><br><br>2) why should routers connected by a point to point link having interface addresses assigned,<br>&nbsp; should advertise a stub link a stub connection to the other router's interface address.<br><br><br>thanks<br
Permalink | Reply | 6 comments |
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Acee Lindem | 6 Oct 2009 17:10

Re: ospf backbone area

Hi Sinbad,
See inline.

On Oct 6, 2009, at 6:20 AM, Sinbad wrote:

>              ...........................
>              .   +                     .
>              .   | 3+---+              .      N12      N14
>              . N1|--|RT1|\ 1           .        \ N13 /
>              .   |  +---+ \            .        8\ |8/8
>              .   +         \ ____      .          \|/
>              .              /    \   1+---+8    8+---+6
>              .             *  N3  *---|RT4|------|RT5|--------+
>              .              \____/    +---+      +---+        |
>              .    +         /      \   .           |7         |
>              .    | 3+---+ /        \  .           |          |
>              .  N2|--|RT2|/1        1\ .           |6         |
>              .    |  +---+            +---+8    6+---+        |
>              .    +                   |RT3|------|RT6|        |
>              .                        +---+      +---+        |
>              .                      2/ .         Ia|7         |
>              .                      /  .           |          |
>              .             +---------+ .           |          |
>              .Area 1           N4      .           |          |
>              ...........................           |          |
>           ..........................               |          |
>           .            N11         .               |          |
>           .        +---------+     .               |          |
>           .             |          .               |          |    N12
>           .             |3         .             Ib|5         |6 2/
>           .           +---+        .             +----+     +---+/
>           .           |RT9|        .    .........|RT10|.....|RT7|--- 
> N15.
>           .           +---+        .    .        +----+     +---+  
> 9    .
>           .             |1         .    .    +  /3    1\      | 
> 1       .
>           .            _|__        .    .    | /        \   __| 
> _       .
>           .           /    \      1+----+2   |/          \ /     
> \      .
>           .          *  N9  *------|RT11|----|            *  N6   
> *     .
>           .           \____/       +----+    |              
> \____/      .
>           .             |          .    .    |                 
> |        .
>           .             |1         .    .    +                | 
> 1       .
>           .  +--+   10+----+       .    .   N8              +--- 
> +      .
>           .  |H1|-----|RT12|       .    .                   | 
> RT8|      .
>           .  +--+SLIP +----+       .    .                   +--- 
> +      .
>           .             |2         .    .                     | 
> 4       .
>           .             |          .    .                      
> |        .
>           .        +---------+     .    .                 +-------- 
> +   .
>           .            N10         .    .                      
> N7       .
>           .                        .    .Area  
> 2                        .
>           .Area  
> 3                  .    ................................
>           ..........................
>
>
>
> 1) In the above ospf topology according to ospf rfc 2328 in section  
> 3.4, it states that
>
>    "Note that a failure of the line between Routers RT6 and RT10
>    will cause the backbone to become disconnected."
>
> Though there is router RT7 in area 2 still connected to the  
> backbone.It confused my understanding of
> disconnected backbone area. Can someone shed some light on this.

I believe this issue has been raised before although I couldn't find  
an errata. The figure is incorrect. Network N8 should be in the  
backbone area rather than Area 2.

>
>
> 2) why should routers connected by a point to point link having  
> interface addresses assigned,
>   should advertise a stub link a stub connection to the other  
> router's interface address.

This dates back to the fact that P2P links were represented as a host  
route to the destination network on BSD based systems. Those of you  
who are familiar with GateD will remember this. Note that there is  
also an option to represent/advertise P2P links as a subnets. Most if  
not all routers vendors advertise the subnet.

Hope this helps,
Acee

>
>
> thanks
>
> _______________________________________________
> OSPF mailing list
> OSPF <at> ietf.org
> https://www.ietf.org/mailman/listinfo/ospf
Permalink | Reply | 5 comments |
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Joakim Tjernlund | 6 Oct 2009 17:22
Picon

Re: ospf backbone area

>
> Hi Sinbad,
> See inline.
>
> On Oct 6, 2009, at 6:20 AM, Sinbad wrote:
>
> >              ...........................
> >              .   +                     .
> >              .   | 3+---+              .      N12      N14
> >              . N1|--|RT1|\ 1           .        \ N13 /
> >              .   |  +---+ \            .        8\ |8/8
> >              .   +         \ ____      .          \|/
> >              .              /    \   1+---+8    8+---+6
> >              .             *  N3  *---|RT4|------|RT5|--------+
> >              .              \____/    +---+      +---+        |
> >              .    +         /      \   .           |7         |
> >              .    | 3+---+ /        \  .           |          |
> >              .  N2|--|RT2|/1        1\ .           |6         |
> >              .    |  +---+            +---+8    6+---+        |
> >              .    +                   |RT3|------|RT6|        |
> >              .                        +---+      +---+        |
> >              .                      2/ .         Ia|7         |
> >              .                      /  .           |          |
> >              .             +---------+ .           |          |
> >              .Area 1           N4      .           |          |
> >              ...........................           |          |
> >           ..........................               |          |
> >           .            N11         .               |          |
> >           .        +---------+     .               |          |
> >           .             |          .               |          |    N12
> >           .             |3         .             Ib|5         |6 2/
> >           .           +---+        .             +----+     +---+/
> >           .           |RT9|        .    .........|RT10|.....|RT7|---
> > N15.
> >           .           +---+        .    .        +----+     +---+
> > 9    .
> >           .             |1         .    .    +  /3    1\      |
> > 1       .
> >           .            _|__        .    .    | /        \   __|
> > _       .
> >           .           /    \      1+----+2   |/          \ /
> > \      .
> >           .          *  N9  *------|RT11|----|            *  N6
> > *     .
> >           .           \____/       +----+    |
> > \____/      .
> >           .             |          .    .    |
> > |        .
> >           .             |1         .    .    +                |
> > 1       .
> >           .  +--+   10+----+       .    .   N8              +---
> > +      .
> >           .  |H1|-----|RT12|       .    .                   |
> > RT8|      .
> >           .  +--+SLIP +----+       .    .                   +---
> > +      .
> >           .             |2         .    .                     |
> > 4       .
> >           .             |          .    .
> > |        .
> >           .        +---------+     .    .                 +--------
> > +   .
> >           .            N10         .    .
> > N7       .
> >           .                        .    .Area
> > 2                        .
> >           .Area
> > 3                  .    ................................
> >           ..........................
> >
> >
> >
> > 1) In the above ospf topology according to ospf rfc 2328 in section
> > 3.4, it states that
> >
> >    "Note that a failure of the line between Routers RT6 and RT10
> >    will cause the backbone to become disconnected."
> >
> > Though there is router RT7 in area 2 still connected to the
> > backbone.It confused my understanding of
> > disconnected backbone area. Can someone shed some light on this.
>
> I believe this issue has been raised before although I couldn't find
> an errata. The figure is incorrect. Network N8 should be in the
> backbone area rather than Area 2.
>
>
> >
> >
> > 2) why should routers connected by a point to point link having
> > interface addresses assigned,
> >   should advertise a stub link a stub connection to the other
> > router's interface address.
>
> This dates back to the fact that P2P links were represented as a host
> route to the destination network on BSD based systems. Those of you
> who are familiar with GateD will remember this. Note that there is
> also an option to represent/advertise P2P links as a subnets. Most if
> not all routers vendors advertise the subnet.

Do you have a choice here? I read the RFC that if the P2P link has
a host route (mask = 255.255.255.255) you have to advertise a stub
link to the other router's interface address.

>
> Hope this helps,
> Acee
Permalink | Reply | 4 comments |
headers
Acee Lindem | 6 Oct 2009 18:07

Re: ospf backbone area

Hi Joakim,



On Oct 6, 2009, at 11:22 AM, Joakim Tjernlund wrote:


Hi Sinbad,
See inline.

On Oct 6, 2009, at 6:20 AM, Sinbad wrote:

             ...........................
             .   +                     .
             .   | 3+---+              .      N12      N14
             . N1|--|RT1|\ 1           .        \ N13 /
             .   |  +---+ \            .        8\ |8/8
             .   +         \ ____      .          \|/
             .              /    \   1+---+8    8+---+6
             .             *  N3  *---|RT4|------|RT5|--------+
             .              \____/    +---+      +---+        |
             .    +         /      \   .           |7         |
             .    | 3+---+ /        \  .           |          |
             .  N2|--|RT2|/1        1\ .           |6         |
             .    |  +---+            +---+8    6+---+        |
             .    +                   |RT3|------|RT6|        |
             .                        +---+      +---+        |
             .                      2/ .         Ia|7         |
             .                      /  .           |          |
             .             +---------+ .           |          |
             .Area 1           N4      .           |          |
             ...........................           |          |
          ..........................               |          |
          .            N11         .               |          |
          .        +---------+     .               |          |
          .             |          .               |          |    N12
          .             |3         .             Ib|5         |6 2/
          .           +---+        .             +----+     +---+/
          .           |RT9|        .    .........|RT10|.....|RT7|---
N15.
          .           +---+        .    .        +----+     +---+
9    .
          .             |1         .    .    +  /3    1\      |
1       .
          .            _|__        .    .    | /        \   __|
_       .
          .           /    \      1+----+2   |/          \ /
\      .
          .          *  N9  *------|RT11|----|            *  N6
*     .
          .           \____/       +----+    |
\____/      .
          .             |          .    .    |
|        .
          .             |1         .    .    +                |
1       .
          .  +--+   10+----+       .    .   N8              +---
+      .
          .  |H1|-----|RT12|       .    .                   |
RT8|      .
          .  +--+SLIP +----+       .    .                   +---
+      .
          .             |2         .    .                     |
4       .
          .             |          .    .
|        .
          .        +---------+     .    .                 +--------
+   .
          .            N10         .    .
N7       .
          .                        .    .Area
2                        .
          .Area
3                  .    ................................
          ..........................



1) In the above ospf topology according to ospf rfc 2328 in section
3.4, it states that

   "Note that a failure of the line between Routers RT6 and RT10
   will cause the backbone to become disconnected."

Though there is router RT7 in area 2 still connected to the
backbone.It confused my understanding of
disconnected backbone area. Can someone shed some light on this.

I believe this issue has been raised before although I couldn't find
an errata. The figure is incorrect. Network N8 should be in the
backbone area rather than Area 2.




2) why should routers connected by a point to point link having
interface addresses assigned,
  should advertise a stub link a stub connection to the other
router's interface address.

This dates back to the fact that P2P links were represented as a host
route to the destination network on BSD based systems. Those of you
who are familiar with GateD will remember this. Note that there is
also an option to represent/advertise P2P links as a subnets. Most if
not all routers vendors advertise the subnet.

Do you have a choice here? I read the RFC that if the P2P link has
a host route (mask = 255.255.255.255) you have to advertise a stub
link to the other router's interface address.

From RFC 2328:

12.4.1.1. Describing point-to-point interfaces For point-to-point interfaces, one or more link descriptions are added to the router-LSA as follows: o If the neighboring router is fully adjacent, add a Type 1 link (point-to-point). The Link ID should be set to the Router ID of the neighboring router. For numbered point-to-point networks, the Link Data should specify the IP interface address. For unnumbered point-to-point networks, the Link Data field should specify the interface's MIB-II [Ref8] ifIndex value. The cost should be set to the output cost of the point-to-point interface. o In addition, as long as the state of the interface is "Point-to-Point" (and regardless of the neighboring router state), a Type 3 link (stub network) should be added. There are two forms that this stub link can take: Option 1 Assuming that the neighboring router's IP address is known, set the Link ID of the Type 3 link to the neighbor's IP address, the Link Data to the mask 0xffffffff (indicating a host route), and the cost to the interface's configured output cost.[15] Option 2 If a subnet has been assigned to the point-to- point link, set the Link ID of the Type 3 link to the subnet's IP address, the Link Data to the subnet's mask, and the cost to the interface's configured output cost.[16] Hope this helps,Acee







Hope this helps,
Acee


<div>
Hi Joakim,<div>
<div><span class="Apple-style-span"><span class="Apple-style-span"><br></span></span></div>
<div><br></div>
<div>
<br><div>
<div>On Oct 6, 2009, at 11:22 AM, Joakim Tjernlund wrote:</div>
<br class="Apple-interchange-newline"><blockquote type="cite">
<blockquote type="cite">
<div><br></div>
<div>Hi Sinbad,</div>
<div>See inline.</div>
<div><br></div>
<div>On Oct 6, 2009, at 6:20 AM, Sinbad wrote:</div>
<div><br></div> <blockquote type="cite">
<div>
<span class="Apple-converted-space">&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>...........................</div>
<div>
<span class="Apple-converted-space">&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>. <span class="Apple-converted-space">&nbsp; </span>+ <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>.</div>
<div>
<span class="Apple-converted-space">&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>. <span class="Apple-converted-space">&nbsp; </span>| 3+---+<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; </span>N12<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; </span>N14</div>
<div>
<span class="Apple-converted-space">&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>. N1|--|RT1|\ 1 <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; </span>\ N13 /</div>
<div>
<span class="Apple-converted-space">&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>. <span class="Apple-converted-space">&nbsp; </span>|<span class="Apple-converted-space">&nbsp; </span>+---+ \<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; </span>8\ |8/8</div>
<div>
<span class="Apple-converted-space">&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>. <span class="Apple-converted-space">&nbsp; </span>+ <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; </span>\ ____<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>\|/</div>
<div>
<span class="Apple-converted-space">&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>/<span class="Apple-converted-space">&nbsp; &nbsp; </span>\ <span class="Apple-converted-space">&nbsp; </span>1+---+8<span class="Apple-converted-space">&nbsp; &nbsp; </span>8+---+6</div>
<div>
<span class="Apple-converted-space">&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>. <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>*<span class="Apple-converted-space">&nbsp; </span>N3<span class="Apple-converted-space">&nbsp; </span>*---|RT4|------|RT5|--------+</div>
<div>
<span class="Apple-converted-space">&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>\____/<span class="Apple-converted-space">&nbsp; &nbsp; </span>+---+<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; </span>+---+<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; </span>|</div>
<div>
<span class="Apple-converted-space">&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; </span>+ <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; </span>/<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; </span>\ <span class="Apple-converted-space">&nbsp; </span>. <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>|7 <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; </span>|</div>
<div>
<span class="Apple-converted-space">&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; </span>| 3+---+ /<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; </span>\<span class="Apple-converted-space">&nbsp; </span>. <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>|<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>|</div>
<div>
<span class="Apple-converted-space">&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; </span>N2|--|RT2|/1<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; </span>1\ . <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>|6 <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; </span>|</div>
<div>
<span class="Apple-converted-space">&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; </span>|<span class="Apple-converted-space">&nbsp; </span>+---+<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>+---+8<span class="Apple-converted-space">&nbsp; &nbsp; </span>6+---+<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; </span>|</div>
<div>
<span class="Apple-converted-space">&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; </span>+ <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>|RT3|------|RT6|<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; </span>|</div>
<div>
<span class="Apple-converted-space">&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>+---+<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; </span>+---+<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; </span>|</div>
<div>
<span class="Apple-converted-space">&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>2/ . <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; </span>Ia|7 <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; </span>|</div>
<div>
<span class="Apple-converted-space">&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>/<span class="Apple-converted-space">&nbsp; </span>. <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>|<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>|</div>
<div>
<span class="Apple-converted-space">&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>. <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>+---------+ . <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>|<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>|</div>
<div>
<span class="Apple-converted-space">&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>.Area 1 <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>N4<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; </span>. <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>|<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>|</div>
<div>
<span class="Apple-converted-space">&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>........................... <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>|<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>|</div>
<div>
<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>.......................... <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>|<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>|</div>
<div>
<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>N11 <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; </span>. <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>|<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>|</div>
<div>
<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; </span>+---------+ <span class="Apple-converted-space">&nbsp; &nbsp; </span>. <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>|<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>|</div>
<div>
<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>. <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>|<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>. <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>|<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>|<span class="Apple-converted-space">&nbsp; &nbsp; </span>N12</div>
<div>
<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>. <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>|3 <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; </span>. <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>Ib|5 <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; </span>|6 2/</div>
<div>
<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>. <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>+---+<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; </span>. <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>+----+ <span class="Apple-converted-space">&nbsp; &nbsp; </span>+---+/</div>
<div>
<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>. <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>|RT9|<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; </span>.........|RT10|.....|RT7|---</div>
<div>N15.</div>
<div>
<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>. <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>+---+<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; </span>+----+ <span class="Apple-converted-space">&nbsp; &nbsp; </span>+---+</div>
<div>9<span class="Apple-converted-space">&nbsp; &nbsp; </span>.</div>
<div>
<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>. <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>|1 <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; </span>+<span class="Apple-converted-space">&nbsp; </span>/3<span class="Apple-converted-space">&nbsp; &nbsp; </span>1\<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; </span>|</div>
<div>1 <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; </span>.</div>
<div>
<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>_|__<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; </span>| /<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; </span>\ <span class="Apple-converted-space">&nbsp; </span>__|</div>
<div>_ <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; </span>.</div>
<div>
<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>. <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>/<span class="Apple-converted-space">&nbsp; &nbsp; </span>\<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; </span>1+----+2 <span class="Apple-converted-space">&nbsp; </span>|/<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>\ /</div>
<div>\<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; </span>.</div>
<div>
<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>*<span class="Apple-converted-space">&nbsp; </span>N9<span class="Apple-converted-space">&nbsp; </span>*------|RT11|----|<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>*<span class="Apple-converted-space">&nbsp; </span>N6</div>
<div>* <span class="Apple-converted-space">&nbsp; &nbsp; </span>.</div>
<div>
<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>. <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>\____/ <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; </span>+----+<span class="Apple-converted-space">&nbsp; &nbsp; </span>|</div>
<div>\____/<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; </span>.</div>
<div>
<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>. <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>|<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; </span>|</div>
<div>|<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; </span>.</div>
<div>
<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>. <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>|1 <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; </span>+<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>|</div>
<div>1 <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; </span>.</div>
<div>
<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; </span>+--+ <span class="Apple-converted-space">&nbsp; </span>10+----+ <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; </span>. <span class="Apple-converted-space">&nbsp; </span>N8<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>+---</div>
<div>+<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; </span>.</div>
<div>
<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; </span>|H1|-----|RT12| <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; </span>. <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>|</div>
<div>RT8|<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; </span>.</div>
<div>
<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; </span>+--+SLIP +----+ <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; </span>. <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>+---</div>
<div>+<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; </span>.</div>
<div>
<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>. <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>|2 <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; </span>. <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>|</div>
<div>4 <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; </span>.</div>
<div>
<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>. <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>|<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; </span>.</div>
<div>|<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; </span>.</div>
<div>
<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; </span>+---------+ <span class="Apple-converted-space">&nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; </span>. <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>+--------</div>
<div>+ <span class="Apple-converted-space">&nbsp; </span>.</div>
<div>
<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>N10 <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; </span>.</div>
<div>N7 <span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; </span>.</div>
<div>
<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; </span>.Area</div>
<div>2<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>.</div>
<div>
<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>.Area</div>
<div>3<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>.<span class="Apple-converted-space">&nbsp; &nbsp; </span>................................</div>
<div>
<span class="Apple-converted-space">&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; </span>..........................</div>
<div><br></div>
<div><br></div>
<div><br></div>
<div>1) In the above ospf topology according to ospf rfc 2328 in section</div>
<div>3.4, it states that</div>
<div><br></div>
<div>
<span class="Apple-converted-space">&nbsp;&nbsp; </span>"Note that a failure of the line between Routers RT6 and RT10</div>
<div>
<span class="Apple-converted-space">&nbsp;&nbsp; </span>will cause the backbone to become disconnected."</div>
<div><br></div>
<div>Though there is router RT7 in area 2 still connected to the</div>
<div>backbone.It confused my understanding of</div>
<div>disconnected backbone area. Can someone shed some light on this.</div> </blockquote>
<div><br></div>
<div>I believe this issue has been raised before although I couldn't find</div>
<div>an errata. The figure is incorrect. Network N8 should be in the</div>
<div>backbone area rather than Area 2.</div>
<div><br></div>
<div><br></div> <blockquote type="cite">
<div><br></div>
<div><br></div>
<div>2) why should routers connected by a point to point link having</div>
<div>interface addresses assigned,</div>
<div>
<span class="Apple-converted-space">&nbsp; </span>should advertise a stub link a stub connection to the other</div>
<div>router's interface address.</div> </blockquote>
<div><br></div>
<div>This dates back to the fact that P2P links were represented as a host</div>
<div>route to the destination network on BSD based systems. Those of you</div>
<div>who are familiar with GateD will remember this. Note that there is</div>
<div>also an option to represent/advertise P2P links as a subnets. Most if</div>
<div>not all routers vendors advertise the subnet.</div> </blockquote>
<div><br></div>
<div>Do you have a choice here? I read the RFC that if the P2P link has</div>
<div>a host route (mask = 255.255.255.255) you have to advertise a stub</div>
<div>link to the other router's interface address.</div>
</blockquote>
<div><br></div>
<div>From RFC 2328:</div>
<div><br></div>
<div>            12.4.1.1.  Describing point-to-point interfaces

                For point-to-point interfaces, one or more link
                descriptions are added to the router-LSA as follows:

                o   If the neighboring router is fully adjacent, add a
                    Type 1 link (point-to-point). The Link ID should be
                    set to the Router ID of the neighboring router. For
                    numbered point-to-point networks, the Link Data
                    should specify the IP interface address. For
                    unnumbered point-to-point networks, the Link Data
                    field should specify the interface's MIB-II [Ref8]
                    ifIndex value. The cost should be set to the output
                    cost of the point-to-point interface.

                o   In addition, as long as the state of the interface
                    is "Point-to-Point" (and regardless of the
                    neighboring router state), a Type 3 link (stub
                    network) should be added. There are two forms that
                    this stub link can take:

                    Option 1
                        Assuming that the neighboring router's IP
                        address is known, set the Link ID of the Type 3
                        link to the neighbor's IP address, the Link Data
                        to the mask 0xffffffff (indicating a host
                        route), and the cost to the interface's
                        configured output cost.[15]

                    Option 2
                        If a subnet has been assigned to the point-to-
                        point link, set the Link ID of the Type 3 link
                        to the subnet's IP address, the Link Data to the
                        subnet's mask, and the cost to the interface's
                        configured output cost.[16]

Hope this helps,Acee</div>
<div><br></div>
<div><br></div>
<div><br></div>
<div><br></div>
<br><blockquote type="cite">
<div><br></div> <blockquote type="cite">
<div><br></div>
<div>Hope this helps,</div>
<div>Acee</div> </blockquote>
<div><br></div> </blockquote>
</div>
<br>
</div>
</div>
</div>
Permalink | Reply | 3 comments |
headers
Joakim Tjernlund | 6 Oct 2009 19:25
Picon

Re: ospf backbone area

>
> Hi Joakim,
>
> On Oct 6, 2009, at 11:22 AM, Joakim Tjernlund wrote:
>
> Hi Sinbad,
> See inline.
>
> On Oct 6, 2009, at 6:20 AM, Sinbad wrote:
>
>              ...........................
>              .   +                     .
>              .   | 3+---+              .      N12      N14
>              . N1|--|RT1|\ 1           .        \ N13 /
>              .   |  +---+ \            .        8\ |8/8
>              .   +         \ ____      .          \|/
>              .              /    \   1+---+8    8+---+6
>              .             *  N3  *---|RT4|------|RT5|--------+
>              .              \____/    +---+      +---+        |
>              .    +         /      \   .           |7         |
>              .    | 3+---+ /        \  .           |          |
>              .  N2|--|RT2|/1        1\ .           |6         |
>              .    |  +---+            +---+8    6+---+        |
>              .    +                   |RT3|------|RT6|        |
>              .                        +---+      +---+        |
>              .                      2/ .         Ia|7         |
>              .                      /  .           |          |
>              .             +---------+ .           |          |
>              .Area 1           N4      .           |          |
>              ...........................           |          |
>           ..........................               |          |
>           .            N11         .               |          |
>           .        +---------+     .               |          |
>           .             |          .               |          |    N12
>           .             |3         .             Ib|5         |6 2/
>           .           +---+        .             +----+     +---+/
>           .           |RT9|        .    .........|RT10|.....|RT7|---
> N15.
>           .           +---+        .    .        +----+     +---+
> 9    .
>           .             |1         .    .    +  /3    1\      |
> 1       .
>           .            _|__        .    .    | /        \   __|
> _       .
>           .           /    \      1+----+2   |/          \ /
> \      .
>           .          *  N9  *------|RT11|----|            *  N6
> *     .
>           .           \____/       +----+    |
> \____/      .
>           .             |          .    .    |
> |        .
>           .             |1         .    .    +                |
> 1       .
>           .  +--+   10+----+       .    .   N8              +---
> +      .
>           .  |H1|-----|RT12|       .    .                   |
> RT8|      .
>           .  +--+SLIP +----+       .    .                   +---
> +      .
>           .             |2         .    .                     |
> 4       .
>           .             |          .    .
> |        .
>           .        +---------+     .    .                 +--------
> +   .
>           .            N10         .    .
> N7       .
>           .                        .    .Area
> 2                        .
>           .Area
> 3                  .    ................................
>           ..........................
>
> 1) In the above ospf topology according to ospf rfc 2328 in section
> 3.4, it states that
>
>    "Note that a failure of the line between Routers RT6 and RT10
>    will cause the backbone to become disconnected."
>
> Though there is router RT7 in area 2 still connected to the
> backbone.It confused my understanding of
> disconnected backbone area. Can someone shed some light on this.
>
> I believe this issue has been raised before although I couldn't find
> an errata. The figure is incorrect. Network N8 should be in the
> backbone area rather than Area 2.
>
> 2) why should routers connected by a point to point link having
> interface addresses assigned,
>   should advertise a stub link a stub connection to the other
> router's interface address.
>
> This dates back to the fact that P2P links were represented as a host
> route to the destination network on BSD based systems. Those of you
> who are familiar with GateD will remember this. Note that there is
> also an option to represent/advertise P2P links as a subnets. Most if
> not all routers vendors advertise the subnet.
>
> Do you have a choice here? I read the RFC that if the P2P link has
> a host route (mask = 255.255.255.255) you have to advertise a stub
> link to the other router's interface address.
>
> From RFC 2328:
>
>             12.4.1.1.  Describing point-to-point interfaces
>
>                 For point-to-point interfaces, one or more link
>                 descriptions are added to the router-LSA as follows:
>
>                 o   If the neighboring router is fully adjacent, add a
>                     Type 1 link (point-to-point). The Link ID should be
>                     set to the Router ID of the neighboring router. For
>                     numbered point-to-point networks, the Link Data
>                     should specify the IP interface address. For
>                     unnumbered point-to-point networks, the Link Data
>                     field should specify the interface's MIB-II [Ref8]
>                     ifIndex value. The cost should be set to the output
>                     cost of the point-to-point interface.
>
>                 o   In addition, as long as the state of the interface
>                     is "Point-to-Point" (and regardless of the
>                     neighboring router state), a Type 3 link (stub
>                     network) should be added. There are two forms that
>                     this stub link can take:
>
>                     Option 1
>                         Assuming that the neighboring router's IP
>                         address is known, set the Link ID of the Type 3
>                         link to the neighbor's IP address, the Link Data
>                         to the mask 0xffffffff (indicating a host
>                         route), and the cost to the interface's
>                         configured output cost.[15]
>
>                     Option 2
>                         If a subnet has been assigned to the point-to-
>                         point link, set the Link ID of the Type 3 link
>                         to the subnet's IP address, the Link Data to the
>                         subnet's mask, and the cost to the interface's
>                         configured output cost.[16]

but mask 255.255.255.255 does not qualify as a subnet? So
that leaves only Option 1

   Jocke
Permalink | Reply | 2 comments |
headers
Acee Lindem | 6 Oct 2009 20:19

Re: ospf backbone area


On Oct 6, 2009, at 1:25 PM, Joakim Tjernlund wrote:

<pruned>

>>
>> 2) why should routers connected by a point to point link having
>> interface addresses assigned,
>>   should advertise a stub link a stub connection to the other
>> router's interface address.
>>
>> This dates back to the fact that P2P links were represented as a host
>> route to the destination network on BSD based systems. Those of you
>> who are familiar with GateD will remember this. Note that there is
>> also an option to represent/advertise P2P links as a subnets. Most if
>> not all routers vendors advertise the subnet.
>>
>> Do you have a choice here? I read the RFC that if the P2P link has
>> a host route (mask = 255.255.255.255) you have to advertise a stub
>> link to the other router's interface address.
>>
>> From RFC 2328:
>>
>>             12.4.1.1.  Describing point-to-point interfaces
>>
>>                 For point-to-point interfaces, one or more link
>>                 descriptions are added to the router-LSA as follows:
>>
>>                 o   If the neighboring router is fully adjacent,  
>> add a
>>                     Type 1 link (point-to-point). The Link ID  
>> should be
>>                     set to the Router ID of the neighboring  
>> router. For
>>                     numbered point-to-point networks, the Link Data
>>                     should specify the IP interface address. For
>>                     unnumbered point-to-point networks, the Link Data
>>                     field should specify the interface's MIB-II  
>> [Ref8]
>>                     ifIndex value. The cost should be set to the  
>> output
>>                     cost of the point-to-point interface.
>>
>>                 o   In addition, as long as the state of the  
>> interface
>>                     is "Point-to-Point" (and regardless of the
>>                     neighboring router state), a Type 3 link (stub
>>                     network) should be added. There are two forms  
>> that
>>                     this stub link can take:
>>
>>                     Option 1
>>                         Assuming that the neighboring router's IP
>>                         address is known, set the Link ID of the  
>> Type 3
>>                         link to the neighbor's IP address, the  
>> Link Data
>>                         to the mask 0xffffffff (indicating a host
>>                         route), and the cost to the interface's
>>                         configured output cost.[15]
>>
>>                     Option 2
>>                         If a subnet has been assigned to the point- 
>> to-
>>                         point link, set the Link ID of the Type 3  
>> link
>>                         to the subnet's IP address, the Link Data  
>> to the
>>                         subnet's mask, and the cost to the  
>> interface's
>>                         configured output cost.[16]
>
> but mask 255.255.255.255 does not qualify as a subnet? So
> that leaves only Option 1

Yes - if you use 255.255.255.255, you will need to support option 1.  
We already have 2 options, we don't need a third.

Acee

>
>    Jocke
>
Permalink | Reply | 1 comment |
headers
Joakim Tjernlund | 6 Oct 2009 20:35
Picon

Re: ospf backbone area


Acee Lindem <acee <at> lindem.com> wrote on 06/10/2009 20:19:25:

> From:
>
> Acee Lindem <acee <at> lindem.com>
>
> To:
>
> Joakim Tjernlund <joakim.tjernlund <at> transmode.se>
>
> Cc:
>
> ospf <at> ietf.org, ospf-bounces <at> ietf.org
>
> Date:
>
> 06/10/2009 20:20
>
> Subject:
>
> Re: [OSPF] ospf backbone area
>
>
> On Oct 6, 2009, at 1:25 PM, Joakim Tjernlund wrote:
>
> <pruned>
>
> >>
> >> 2) why should routers connected by a point to point link having
> >> interface addresses assigned,
> >>   should advertise a stub link a stub connection to the other
> >> router's interface address.
> >>
> >> This dates back to the fact that P2P links were represented as a host
> >> route to the destination network on BSD based systems. Those of you
> >> who are familiar with GateD will remember this. Note that there is
> >> also an option to represent/advertise P2P links as a subnets. Most if
> >> not all routers vendors advertise the subnet.
> >>
> >> Do you have a choice here? I read the RFC that if the P2P link has
> >> a host route (mask = 255.255.255.255) you have to advertise a stub
> >> link to the other router's interface address.
> >>
> >> From RFC 2328:
> >>
> >>             12.4.1.1.  Describing point-to-point interfaces
> >>
> >>                 For point-to-point interfaces, one or more link
> >>                 descriptions are added to the router-LSA as follows:
> >>
> >>                 o   If the neighboring router is fully adjacent,
> >> add a
> >>                     Type 1 link (point-to-point). The Link ID
> >> should be
> >>                     set to the Router ID of the neighboring
> >> router. For
> >>                     numbered point-to-point networks, the Link Data
> >>                     should specify the IP interface address. For
> >>                     unnumbered point-to-point networks, the Link Data
> >>                     field should specify the interface's MIB-II
> >> [Ref8]
> >>                     ifIndex value. The cost should be set to the
> >> output
> >>                     cost of the point-to-point interface.
> >>
> >>                 o   In addition, as long as the state of the
> >> interface
> >>                     is "Point-to-Point" (and regardless of the
> >>                     neighboring router state), a Type 3 link (stub
> >>                     network) should be added. There are two forms
> >> that
> >>                     this stub link can take:
> >>
> >>                     Option 1
> >>                         Assuming that the neighboring router's IP
> >>                         address is known, set the Link ID of the
> >> Type 3
> >>                         link to the neighbor's IP address, the
> >> Link Data
> >>                         to the mask 0xffffffff (indicating a host
> >>                         route), and the cost to the interface's
> >>                         configured output cost.[15]
> >>
> >>                     Option 2
> >>                         If a subnet has been assigned to the point-
> >> to-
> >>                         point link, set the Link ID of the Type 3
> >> link
> >>                         to the subnet's IP address, the Link Data
> >> to the
> >>                         subnet's mask, and the cost to the
> >> interface's
> >>                         configured output cost.[16]
> >
> > but mask 255.255.255.255 does not qualify as a subnet? So
> > that leaves only Option 1
>
> Yes - if you use 255.255.255.255, you will need to support option 1.
> We already have 2 options, we don't need a third.

Maybe I read too much into this statement:
 "This dates back to the fact that P2P links were represented as a host
  route to the destination network on BSD based systems. Those of you
  who are familiar with GateD will remember this. Note that there is
  also an option to represent/advertise P2P links as a subnets. Most if
  not all routers vendors advertise the subnet."
I got the impression that you meant that you could choose to advertise P2P/32
with Option 2 instead of Option 1. I guess I read too much into it :)
Permalink | Reply | 0 comments |
headers
Acee Lindem | 21 Oct 2009 17:25
Picon
Favicon

Re: Multi-Topology/Instance OSPFv3 for IPv4-mapped IPv6

Hi Mohamed,
Perhaps a single draft would have sufficed. 
Thanks,
Acee 

|-----Original Message-----
|From: ospf-bounces <at> ietf.org [mailto:ospf-bounces <at> ietf.org] On 
|Behalf Of mohamed.boucadair <at> orange-ftgroup.com
|Sent: Wednesday, October 21, 2009 9:52 AM
|To: Acee Lindem; behave <at> ietf.org; ospf <at> ietf.org
|Subject: Re: [OSPF] Multi-Topology/Instance OSPFv3 for IPv4-mapped IPv6
|
|
|Dear Acee, all,
|
|Actually, no. Two drafts have been submitted: one for 
|multi-topology and another one for multi-instance. We don't 
|want to make any choice about the use of MT or MI. It is up to 
|the SP's taste.
|
|Sorry for the confusion.
|
|Cheers,
|Med 
|
|
|-----Message d'origine-----
|De : Acee Lindem [mailto:acee.lindem <at> ericsson.com] Envoyé : 
|mercredi 21 octobre 2009 15:07 À : BOUCADAIR Mohamed 
|NCPI/NAD/TIP; behave <at> ietf.org; ospf <at> ietf.org Objet : RE: 
|Multi-Topology/Instance OSPFv3 for IPv4-mapped IPv6
|
|Hi Mohamed,
|I take it then that draft-boucadair-ospf-v4v6-ospfv3-mi-01.txt 
|was a misnamed version of 
|draft-boucadair-ospf-v4v6-ospfv3-mt-01.txt and should be 
|ignored. Correct? 
|Thanks,
|Acee 
||-----Original Message-----
||From: ospf-bounces <at> ietf.org [mailto:ospf-bounces <at> ietf.org] On 
|Behalf Of 
||mohamed.boucadair <at> orange-ftgroup.com
||Sent: Wednesday, October 21, 2009 2:07 AM
||To: behave <at> ietf.org; ospf <at> ietf.org
||Subject: [OSPF] Multi-Topology/Instance OSPFv3 for IPv4-mapped IPv6
||
|| 
||Dear all,
||
||FYI. We submitted the following draft.
||
||Comments are more than welcome.
||
||Cheers,
||Med
||
||-----Message d'origine-----
||De : i-d-announce-bounces <at> ietf.org
||[mailto:i-d-announce-bounces <at> ietf.org] De la part de 
||Internet-Drafts <at> ietf.org Envoyé : mardi 20 octobre 2009 13:45 À :
||i-d-announce <at> ietf.org Objet : I-D
||Action:draft-boucadair-ospf-v4v6-ospfv3-mt-01.txt
||
||A New Internet-Draft is available from the on-line Internet-Drafts 
||directories.
||
||	Title           : Multi-Topology OSPFv3 for IPv4-mapped IPv6
||	Author(s)       : M. Boucadair, et al.
||	Filename        : draft-boucadair-ospf-v4v6-ospfv3-mt-01.txt
||	Pages           : 7
||	Date            : 2009-10-20
||
||This memo defines two new Multi Topology Routing Identifiers (MT IDs) 
||in OSPFv3 [RFC2740]).  These new MT-OSPFv3 [I-D.ietf-ospf-mt-ospfv3] 
||topologies are meant to convey routing information which is 
|restricted 
||to IPv4-mapped IPv6 addresses [I-D.ietf-behave-address-format].  The 
||goal of running separate instances for IPv4-mapped IPv6 routes is to 
||isolate the IPv6 routing table from the IPv4 routing table, and to 
||avoid any overload due to the population of the table by 
|IPv4-inferred 
||routes.  This isolation is motivated also from an operational 
||perspective to enforce specific routing policies for each topology.
||
||A URL for this Internet-Draft is:
||http://www.ietf.org/internet-drafts/draft-boucadair-ospf-v4v6-o
||spfv3-mt-01.txt
||
||The URL for the multi-instance draft is:
||http://www.ietf.org/internet-drafts/draft-boucadair-ospf-v4v6-o
||spfv3-mi-01.txt
||
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||Any unauthorised use or dissemination is prohibited.
||Messages are susceptible to alteration. 
||France Telecom Group shall not be liable for the message if altered, 
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||If you are not the intended addressee of this message, please 
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|If you are not the intended addressee of this message, please 
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rfc-editor | 23 Oct 2009 01:44
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RFC 5709 on OSPFv2 HMAC-SHA Cryptographic Authentication


A new Request for Comments is now available in online RFC libraries.

        
        RFC 5709

        Title:      OSPFv2 HMAC-SHA Cryptographic Authentication 
        Author:     M. Bhatia, V. Manral,
                    M. Fanto, R. White,
                    M. Barnes, T. Li,
                    R. Atkinson
        Status:     Standards Track
        Date:       October 2009
        Mailbox:    manav <at> alcatel-lucent.com, 
                    vishwas <at> ipinfusion.com, 
                    mfanto <at> aegisdatasecurity.com,
                    riw <at> cisco.com, 
                    mjbarnes <at> cisco.com,
                    tony.li <at> tony.li, 
                    rja <at> extremenetworks.com
        Pages:      14
        Characters: 30221
        Updates:    RFC2328

        I-D Tag:    draft-ietf-ospf-hmac-sha-07.txt

        URL:        http://www.rfc-editor.org/rfc/rfc5709.txt

This document describes how the National Institute of Standards and
Technology (NIST) Secure Hash Standard family of
algorithms can be used with OSPF version 2's built-in, cryptographic
authentication mechanism.  This updates, but does not supercede,
the cryptographic authentication mechanism specified in RFC 2328.
[STANDARDS TRACK]

This document is a product of the Open Shortest Path First IGP Working Group of the IETF.

This is now a Proposed Standard Protocol.

STANDARDS TRACK: This document specifies an Internet standards track
protocol for the Internet community,and requests discussion and suggestions
for improvements.  Please refer to the current edition of the Internet
Official Protocol Standards (STD 1) for the standardization state and
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