[Xorp-users] IPv6 & BGP

[Hasso Tepper]

Atanu Ghosh wrote:
> >>>>> "Hasso" == Hasso Tepper <hasso@linux.ee> writes:
> Actually this is not a protocol issue but a configuration issue. In the
> configuration we have an IPv4 nexthop marked as a mandatory item. In
> the case where you want to use BGP for IPv6 only we have no way of
> disabling the check (yet).

The need to specify next-hop explicitly in the configuration even in the 
IPv4 case is very strange requirement IMHO. Never seen it in any other 
implementation. The address used in NEXT_HOP attribute should be normally 
derived from interface address used for BGP session (local-ip in XORP). 
5.1.3 section in draft-ietf-idr-bgp4-26 should give quite good rules for 
that. In case there is need to disregard these rules, modifying nexthop 
is job of policies.

> If you set the ipv4-unicast and ipv4-multicast flags to false and you 
> have no local IPv4 addresses then just choose a legal IPv4 address. The 
> IPv4 nexthop address should *not* be used it just needs to satisify the 
> configuration constraint. I have never tried an IPv6 peering on a 
> machine that does not have any IPv4 addresses configured but I would 
> expect it to work. 

Note, that there is still need to have the IPv4 unicast address in the BGP 
speaker. Even RFC2858bis states:

"This document assumes that any BGP speaker (including the one that 
supports multiprotocol capabilities defined in this document) has to have 
an IPv4 address (which will be used, among other things, in the 
AGGREGATOR attribute)."

And the router id MUST be valid IPv4 unicast address as well.


-- 
Hasso Tepper