[j-nsp] Parallel BGP sessions for v6 prefixes over v4 and v6

[Andrey Kostin]

Alexandre Snarskii писал(а) 2024-07-09 07:25:
> On Mon, Jul 08, 2024 at 11:33:48AM -0400, Andrey Kostin via juniper-nsp 
> wrote:
> [...]
>> The problem here is that route-reflector selects a path with ipv4 
>> mapped
>> nexthop and advertises it over ipv6 session. I'm wondering, is anybody
>> already encountered this problem and found a solution how to make a RR
>> to advertise paths with a correct nexthop?
> 
> Have you considered making your inet6 sessions not unicast but 
> labeled-unicast
> explicit-null too ? I guess it may prevent bgp from losing label..
> 

No, I didn't, thanks for the clue. In this case if v6 prefix with v4 
mapped next-hop is advertised via v6 session it should have VPN label 
(explicit-null) and potentially could work in the same way as inet6 
labeled-unicast over v4 session. This is an interesting idea, however 
I'd like to have a plain v6 session as a backup in case if MPLS 
forwarding path isn't available for any reason. Like with v4, if MPLS 
path can't be established, forwarding can always fallback to plain IP. I 
understand though, that having only label 2 attached to v6 packets 
probably would work, although the label will be removed and added again 
on every hop a packet passes. On the other hand, we're in the process of 
implementing SR-ISIS, so this change would be a move in the opposite 
direction, so I'd prefer to keep v6 session in it's natural state. 
Anyways, thank you for the advice!

Kind regards,
Andrey