Choice of address for IPv6 default gateway

Mohacsi Janos mohacsi at
Thu Jan 26 08:18:21 UTC 2012

On Wed, 25 Jan 2012, Daniel STICKNEY wrote:

> I'm having trouble finding authoritative sources on the best common
> practice (if there even is one) for the choice of address for an IPv6
> default gateway in a production server environment (not desktops). For
> example in IPv4 it is common to chose the first or last address in the
> subnet (.1 or .254 for example) as the VIP for VRRP/HSRP. I'm interested
> in input from production environments and or ARIN/RIPE/IANA/etc or top
> vendors.
> I've seen some documentation using <prefix>::1 with either a global
> prefix or link-local (fe80::1). Anyone use either of these in production
> and have negative or positive feedback? fe80::1 is seductive because it
> is short and the idea of having the same default gateway configured
> everywhere might be simple. At the same time using the same address all
> around the network seems to invite confusion or problems if two
> interfaces with the address ever ended up in the same broadcast domain.

Up to your taste. Most cases it is recommended to use link-local default 
gateway. If you use the same address - even link local - your node should 
complain about the duplicate address on the same link. You can rely on the 
autoconfigured link-local address for default gateways (and use RA).

> What about using RAs to install the default route on the servers? The
> 'priority' option (high/medium/low) easy fits with an architecture using
> an active/standby router setup where the active router is configured
> with the 'high' priority and the standby 'medium'. With the timeout
> values tuned for relatively rapid (~3 seconds)  failover this might be
> feasible. Anyone use this in production?

Yes we are using NUD (and using RA to install default gateway) to switch 
from primary rotuer to secondary - due to no VRRP support on a particular 
platform. But in case of RA usage you should also use RA-guard especially 
if you don't have full control on servers connected to your switches.

> I note that VRRPv3 (and keepalived) and HSRP both support IPv6. Since we
> use VRRP for IPv4, using it for IPv6 would keep our architecture the
> same, which has merit too.

If you want consistent and more predictable behavoir use VRRP or maybe 
HSRP if your vendor supports it.
 	Best Regards,
 			Janos Mohacsi

More information about the NANOG mailing list