Subject: Re: [VRRP] VRRP for IPv6 - addresses

From: Bob Hinden <[email-masked]>
Date: Fri, 13 Feb 2004 11:25:07 -0800

John,

>In the current draft for VRRP for IPv6 (draft-ietf-vrrp-ipv6-spec-05.txt),
>the virtual IP address is always a link local address. This is okay
>for a box performing only as a router. However, for applications
>running on a box, this may not be sufficient. For applications like
>VPN that would like to failover the VPN endpoint, the virtual IP
>address must be a globally reachable address. The current draft does

This seems like a reasonable change to me.  It was a feature that was in 
VRRP (for IPv4).  I didn't include it in VRRP for IPv6 because all host to 
router traffic used the routers link-local addresses.  You point out that 
when using things like VPN it also useful to visualize the routers other 
addresses.

The changes to the draft are fairly easy and I should be able to include 
them in the draft I am planning to submit later today.

>not support it. Also, an interface may belong to multiple subnets
>and we may want more than one address belonging to that interface to be
>backed up by another router. This implies that we may need support in the
>VRRP packet to carry multiple virtual IP addresses.

This isn't quite right.  In IPv6 the routers tell the hosts (via router 
advertisements) what prefixes are on the link and that they are the 
router.  So while there may be multiple prefixes (i.e.,  subnets) on the 
link, hosts don't send their off-link traffic to the routers address on the 
prefix, they only send their off-link traffic to the routers link-local 
address.  The result is that one router may back up another router 
independent of the number of subnets on the link.

Nonetheless, I think that the change you suggest for supporting VPNs is a 
good idea and will plan to make the change in the draft.  It won't require 
more than the link-local address to be carried, so it shouldn't impose any 
overhead, other than having to set a count field in the header to 1, on 
people who don't want to use this feature.

Bob

Bob

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From: [email-masked] (Jun-ichiro itojun Hagino)
Date: Sat, 14 Feb 2004 08:10:10 +0900 (JST)

> when using things like VPN it also useful to visualize the routers other 

	vrrp = virtual "ROUTER" redundancy protocol.  you at least need
	a new name...

itojun