[quagga-users 12946] Prefer "local" BGP route over OSPF redistributed

headers Doug Warner | 10 Aug 2012 23:00 · /multiple/

We are transitioning a large OSPF area 0 network to be linked by iBGP.  The
OSPF is bridged together by VPN tunnels and I've set an ospf cost on the VPN
interfaces to be 100 so they are preferred less over the local routes and make
the longer links actually seem longer.

I'm trying to bring a VPN tunnel from a new location into two locations that
are already running OSPF between them, but one endpoint is ending up having
the route preferred all the time, so the other location routes everything
across the VPN to go out that BGP'd link.

Some art might help:
                             10.128.0.0/22
                    ----------- SFJ
                   /             |
10.134.0.0/22     / gre/iBGP     |
RZC              /           gre/OSPF (cost 100)
                 \               |
                  \ gre/iBGP     |
                   \             |
                    ----------- ATL
                             10.136.0.0/24

What I'm seeing is:
-- SFJ will see the iBGP from RZC and announce it into OSPF

# show ip route 10.138.0.0
Routing entry for 10.138.0.0/22
  Known via "bgp", distance 200, metric 1, best
  Last update 00:36:55 ago
  * 172.31.254.29, via gre1

# show ip bgp 10.138.0.0
BGP routing table entry for 10.138.0.0/22
Paths: (1 available, best #1, table Default-IP-Routing-Table)
  Not advertised to any peer
  Local
    172.31.254.29 (metric 1) from 172.31.254.29 (10.138.0.253)
      Origin incomplete, metric 1, localpref 100, valid, internal, best
      Last update: Fri Oct  1 10:13:32 1971

-- ATL will see the iBGP from RZC, but prefer the OSPF routes from SFJ

# show ip route 10.138.0.0
Routing entry for 10.138.0.0/22
  Known via "ospf", distance 110, metric 210, best
  Last update 00:11:10 ago
  * 172.31.254.137, via gre1

# show ip bgp 10.138.0.0
BGP routing table entry for 10.138.0.0/22
Paths: (2 available, best #2, table Default-IP-Routing-Table)
  Advertised to non peer-group peers:
  172.31.254.31
  Local
    172.31.254.31 (metric 1) from 172.31.254.31 (10.138.0.253)
      Origin incomplete, metric 1, localpref 100, valid, internal
      Last update: Fri Aug 10 15:39:05 2012

  Local
    172.31.254.137 from 0.0.0.0 (10.136.0.248)
      Origin incomplete, metric 210, localpref 100, weight 32768, valid,
sourced, best
      Last update: Fri Aug 10 16:08:45 2012

Any ideas if what I'm trying to do here is possible?
And as an aside, I'd even like to have /multiple/ gre tunnels running BGP
between colos and use ECMP via OSPF between them if I can (that's the main
reason we have a large area 0 currently).

-Doug

[quagga-users 12946] Prefer "local" BGP route over OSPF redistributed route