Redistribution of BGP path via OSPF

Nico Schottelius nico.schottelius at ungleich.ch
Sat Dec 28 13:22:53 CET 2019


Good morning,

we have setup OSPF internally to redistribute all of our routes and it
seems that we lose the as path on the way:

          BGP               OSPF               BGP
upstream1 -- router1.place6 --- router2.place5 --- upstream2
                   |
                   | BGP
              internal peer

The routes that are announced by router2.place5 do not contain the AS
path of the "internal peer" anymore, as shows the output of router2.place5:

bird> show route all XX::/48
Table master6:
XX::/48  unicast [ospf_v6 12:01:06.457] E2 (150/5/10000) [147.78.195.251]
        via fe80::21b:21ff:febc:7c80 on bond0.8
        Type: OSPF-E2 univ
        OSPF.metric1: 5
        OSPF.metric2: 10000
        OSPF.tag: 0x00000000
        OSPF.router_id: 147.78.195.251

This way, when we re-announce XX::/48 to upstream2, it looks like as if
we announce that from our ASN, instead of the ASN from the internal
peer.

At the moment we export all routes via OSPF, internal and external.

How do I tell ospf to forward (tag?) the externally received bgp routes
and use that information on the other site?

Best regards,

Nico



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