[f-nsp] BGP - CER2K and looking glass

[Nick Hilliard]

On 03/08/2012 15:01, Alain Hebert wrote:
>     Our issues is that some CER2k are receiving routes from more than 1
> peer and we're trying to then re-advertise them into the Looking Glass
> servers.

Hi Alain,

You need to understand how BGP works.  When a router is sent from one RIB
to another, it goes like this:

router 1:
1. prefix in Loc-RIB of
2. outbound prefix filtering / route-maps / etc
3. prefix "moved" to Adj-RIB-Out on
4. encoded over line protocol on
5. sent to port 179 on router 2

router 2:
6. line protocol is decoded on
7. prefix "moved" to Adj-RIB-In
8. inbound prefix filtering / route-maps / etc
9. best path calculation performed for this prefix; best path operates on
the same prefixes.
10. result of best path calculation is moved to Loc RIB on router 2

So what you're looking for is a copy of adj-rib-in on router 2 to be sent
to your looking glass.  But that isn't possible because the only prefixes
you'll get out of your CER are the results of the best path calculation in
step 10.

It may look strange that you can't tap into the adj-rib-in data sets, but
it guarantees bgp state consistency.

It would probably be possible to do what you're trying to do with the bgp
add-path feature, but this is a relatively new feature and only supported
on recent versions of junos, very recent versions of IOS and IOS-XR >
4.1.0.  I.e. Brocade don't yet support it on their netiron code base.

Nick