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Re: Misconceptions, was: IPv6 RA vs DHCPv6 - The chosen one?
From: Kevin Loch <kloch () kl net>
Date: Fri, 30 Dec 2011 11:47:35 -0500

Steven Bellovin wrote:

VRRP?  The Router Discovery Protocol (RFC 1256).  But given
how much more reliable routers are today than in 1984, I'm
not convinced it's that necessary these days.

VRRP is an absolutely essential protocol in today's Internet.  We use
it on every non-bgp customer port.  Routers still have routing and
performance issues, hardware failures and routine software upgrades.
The layer2 infrastructure between the routers and the customer is also
susceptible to various hardware/software/maintenance problems and fiber
cuts and VRRP can help work around some of those.  A nice side benefit
is the virtual mac addresses that allow for migration to new routers
without the mac address of the default gateway changing.

One key advantage of VRRP over RA's is that you can have multiple
instances on the same layer2 network (vlan) with different functions.

It is very common to have different "routers" (routers, firewalls or
load balancers) on the same vlan with different functions in hosting
environments.  It is also sometimes necessary to have multiple default
gateways on the same vlan for load balancing or traffic engineering.
RA/auto configuration is incompatible with all but the most trivial
configurations.

- Kevin


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