OER doesn't take BGP default as parent?

Hi,

Recently I was playing with Cisco OER. In general it works like magic, but sometimes you can hit the wall trying to understand its behavior :(
This time it happened with default BGP parent route.

Cisco documentation everywhere says: "a parent route — an exact matching route, or a less specific route — in any IP Routing Information Base (RIB). The BGP routing table is searched first, followed by the static routing table, and finally the RIB."

I configured for border router to get default BGP route, but somehow OER doesn't see it. Debug shows the following:

Here we receive default from BGP peer:

Mar 22 10:01:29.831: RT: Try lookup less specific 21.21.10.10/32, default 1
Mar 22 10:01:29.831: RT: Found subnet on less specific 21.21.10.10/32
Mar 22 10:01:29.831: RT: add 0.0.0.0/0 via 21.21.10.10, bgp metric [200/0]
Mar 22 10:01:29.831: RT: NET-RED 0.0.0.0/0
Mar 22 10:01:29.831: RT: default path is now 0.0.0.0 via 21.21.10.10
Mar 22 10:01:29.831: RT: new default network 0.0.0.0
Mar 22 10:01:29.831: RT: NET-RED 0.0.0.0/0

Here OER is trying to create policy and fails with reason "No nexthop in routing tables". What does it mean?

Mar 22 10:01:54.979: OER BR PBR: No nexthop in routing tables
Mar 22 10:01:54.979: OER BR PBR: Control application failed, error: OER PBR no nexthop
Mar 22 10:01:55.247: OER BR PBR(det): remove app: 0.0.0.0/0, ip prot 17, dst opr 7 , src opr 7, 1 65535 1 65535src addr 21.21.55.0/24, dscp 184/4

Regards,
ivan

Comments

  • Maybe the BGP next-hop is more than one hop away? I believe that is a limitation when performing PBR OER. 

  • Good point. In fact, it is so now. But I tested configuration when default route comes to borderd via eBGP session from directly connected routers. The same result.

    Long story (lots of tests), but for the moment I believe the problem is in recursive loop prevention built in OER, when route 0/0 resolves through subset of itslef. It could not be any other way, sure, but in case of OER it somehow (feature? bug?) ignores more specific BGP routes in routing table. If we could somehow point BGP default not via IP address, but via interface?

  • Any new results on this? Curious to know what the problem was? 

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