[VRRP] RFC5798 requires usage of RAs?

Daniel Roesen <dr@cluenet.de> Fri, 15 April 2011 08:57 UTC

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Date: Fri, 15 Apr 2011 10:57:09 +0200
From: Daniel Roesen <dr@cluenet.de>
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Subject: [VRRP] RFC5798 requires usage of RAs?
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Hi,

JUNOS (Juniper router firmware) issues warnings when committing config
changes, noting that RAs are not configured for an interface where VRRP
for IPv6 is configured:

vrrpd[15299]: %CONFLICT-0-WARNING: 'router-advertisement' is not configured
for interface ge-9/2/2.662

RFC5798 states:

6.4.3.  Master
...
         (630) ++ MUST send ND Router Advertisements for the virtual
         router.

That makes no sense to us when RAs are generally not used on the
segment, and hosts are manually configured to point to the VRRP virtual
address as default gateway. We do not want to use RAs in some scenarios
at all.

I've found an older posting on this list, where someone raised the same
question (Q-2):
http://www.ietf.org/mail-archive/web/vrrp/current/msg00763.html

John Cruz' answer seems to clarify, but noone seemed to have envisioned
that the spec lingo actually motivates vendors to assume RAs as being
mandatory when implementing VRRPv6... :-/

RFC5798 states in the introductory section about IPv6 (1.3):

   IPv6 hosts on a LAN will usually learn about one or more default
   routers by receiving Router Advertisements sent using the IPv6
   Neighbor Discovery (ND) protocol [RFC4861].

Given that it says "usually", it recognizes that there are scenarios
where RAs are NOT being used. Unfortunately several bits of language in
the RFC doesn't reflect that, so I would like to suggest changing
specifically rule 630 and section 8.2.3 to reflect no-RA scenarios.

Best regards,
Daniel