RE: VRRP version 3 and IPv6 Neighbor discovery RouterAdvertisement
<John.Cruz <at> nokia.com>
2004-06-29 21:48:02 GMT
I agree that only hosts that are not statically
configured will configure themseleves based on the
ND Router Advertisements. I think that if multiple
VRs are configured for the purpose of load balancing,
then ALL the hosts will be statically configured.
If this is true, then why couple VRRP and ND RA.
My main concern with coupling VRRP and ND router
advertisement in the increased complexity of the ND
implementation. If the situation was "either send
ND RA or don't send", then things are simple. However,
in the presence of multiple VRs, things get complicated.
A router must look at the VRs for which it the master.
If the virtual IP address is something that it is
backing up (because the current master is down), the it must
send out a ND RA on the address owners behalf. It must do this
for each VR. This implies that all routers are configured
similarly. As per the ND RFC, a router will send out only
one RA per interface. In this situation a router may have
to send out more than one RA per interface. I think the
complexity of the ND protocol will be increased just by
coupling it with VRRP.
> -----Original Message-----
> From: ext Don Provan [mailto:dprovan <at> bivio.net]
> Sent: Tuesday, June 29, 2004 11:39 AM
> To: Cruz John (Nokia-ES/MTview)
> Cc: vrrp <at> ietf.org
> Subject: RE: [VRRP] VRRP version 3 and IPv6 Neighbor discovery
> NDs are sent to pick up any nodes which are not configured
> for load balancing. Nodes configured to use a specific router
> in order to achieve load balancing shouldn't be affected
> by NDs for other routers except when their configured
> router is not available.
> This observation has nothing to do with VRRP: it is just
> as true for a non-VRRP network with redundant routers. So
> I'm not seeing what specifically about VRRP is concerning
> -don provan
> dprovan <at> bivio.net
> > -----Original Message-----
> > From: vrrp-bounces <at> ietf.org
> [mailto:vrrp-bounces <at> ietf.org]On Behalf Of
> > John.Cruz <at> nokia.com
> > Sent: Monday, June 28, 2004 1:56 PM
> > To: vrrp <at> ietf.org
> > Subject: [VRRP] VRRP version 3 and IPv6 Neighbor discovery
> > RouterAdvertisement
> > Consider the following scenario
> > ------------------------ N
> > | |
> > | |
> > R1 R2
> > If the routers R1 and R2 are not running VRRP,
> > then both routers send out ND Router advertisements.
> > With auto-configuration, all hosts on the network N
> > would choose one of the routers as their default
> > router. When the current default router fails, the
> > hosts pick the other one as their default router.
> > With VRRPv3, only the master sends out ND router
> > advertisements. All the hosts on the network will set
> > their default router to the virtual IP address. When
> > the current master fails, the backup will become the
> > new master, continue to send out ND router advertisements
> > and will back-up the virtual IP address currently being
> > used by the hosts.
> > All the above makes sense when there is only one virtual
> > router configured. The VRRPv3 spec suggests that for
> > load balancing purposes, one can configure multiple VRs.
> > Let us say that we have two virtual routers configured,
> > VR1 and VR2, and let the virtual IP addresses for the
> > virtual router be VIP1 and VIP2. If VIP1 is the interface
> > address of R1 and VIP2 is the interface address of R2,
> > the, by default, R1 will be master for VR1 and R2 will
> > be master for VR2.
> > Since both R1 and R2 are masters, both will send out
> > ND router advertisements. All the hosts on the network
> > will choose one of the advertisements and therefore
> > choose one of the routers to be their default router.
> > If this happens, then there is no load balancing. The
> > purpose of configuring 2 virtual routers is lost.
> > If the hosts on the network are not auto-configured, then
> > we can configure default routes on some hosts to point
> > to R1 and the remaining to R2 to acheive load balancing.
> > I think that coupling ND router advertisements with
> > VRRP makes sense only if there is one virtual router. If
> > there are multiple virtual routers, then ND router
> > advertisements should not be send out as this will mess
> > with VRRP - basically, hinder load balancing. Note that
> > in IPv4 case (VRRP version 2), VRRP and Router Discovery
> > are not coupled.
> > Any comments?
> > John
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