[c-nsp] route-target import on non-leaking PEs

[Phil Mayers]

On 13/12/12 14:47, Jason Lixfeld wrote:
>>
>> Yes. In fact, that's *required* if you want to do multi-path.
>
> I seem to do multi-path just fine with maximum-paths ibgp 2 on my RR
> clients inside a VRF that sees a default sourced from two different
> RRs.  Said VRF has a common RD between the two PEs.
>
> How is that different?

Well, AIUI multipath *ought* to require unique RDs. Obviously not; I 
wonder how that's working for you?

Basically, as I'm sure you are aware, without "add paths" support, BGP 
can only advertise one copy of a route - any "update" for a route 
implicitly "withdraw"s a previous route.

Therefore, if your RR sends:

update nh=x.x.x.x nlri=65000:1:192.0.2.0/24
update nh=y.y.y.y nlri=65000:1:192.0.2.0/24

...then the 2nd update should wipe the first. This is why (in theory) 
multipath requires a unique RD:

update nh=x.x.x.x nlri=65000:1:192.0.2.0/24
update nh=y.y.y.y nlri=65000:2:192.0.2.0/24

...are different routes.

Out of curiosity, what does:

sh ip bgp vpnv4 vrf XXX net/mask
sh ip cef vrf XXX net/mask detail

...say for one of your working multipath prefixes?