Hi Everyone,

I'm running 6.44, and now attempting to turn on OSPF for route distribution between two routers. Pretty simple setup:

rb01:

• ether1: DHCP WAN
• bridge1: 172.16.42.0/24, 172.16.43.0/30, 172.27.0.0/24
• The 172.16.43.0 is being used for an IP-IP tunnel to rb02 via WAN
• Static routes are in place and working

rb02:

• ether1: DHCP WAN
• bridge1: 172.16.44.0/24, 172.16.43.0/30
• The 172.16.43.0 is being used for an IP-IP tunnel to rb01 via WAN
• Static routes are in place and working

When I enable OSPF and add those networks, the OSPF interfaces are dynamically added and start LSAs.

The neighbor shows up right away, but as soon as that happens, the IP-IP tunnel starts flapping constantly. If I remove the networks from OSPF, the tunnel is stable again.

Right now I have kept the static routes in-place, and they're being redistributed. I had planned to see OSPF being stable, and then start removing the static routes one-by-one.

Any idea why the OSPF adjacency would make the tunnel flap?

Thanks!

are you advertising the tunnel endpoint IPs via OSPF?!
check something like "redistribute connected routes" etc.

are you advertising the tunnel endpoint IPs via OSPF?!
check something like "redistribute connected routes" etc.

Yes, that was it! I had redistribute-connected=yes. The manual isn't clear on why this would break in my situation. Can you explain why it caused the ipip tunnel to flap?

The manual isn't clear on why this would break in my situation. Can you explain why it caused the ipip tunnel to flap?

I imagine it would be something similar to this. I had a similar issue with BGP over an EoIPv6 tunnel.

You are establishing BGP over the tunnel, BGP installs routes and tries to route traffic over the tunnel including tunnel traffic itself, which causes internal loop. Add static route to tunnel remote end to fix the problem.