BGP and OSPF issues

cjw · ‎03-03-2010

Greetings:

We have a mixed BGP and OSPF routing environment. The routing protocol on the MPLS and point to point T-1s is mostly BGP with some OSPF (but moving to BGP). A vendor of ours to whom we have a WAN link advertises via OSPF (and can not advertise via BGP). This link is in a DMZ off of the firewall which advertises the OSPF. There are backup paths to the remote locations via VPN tunnels.

When a WAN link goes down, the lower cost BGP route (from the WAN router) is deselected, and the higher cost OSPF route (from the firewall) is selected. This happens dynamically.

When the WAN link comes back up the higher OSPF route is NOT dynamically deselected in favor of the BGP route. Instead, we must clear the OSPF process on the WAN routers.

So that every location knows all the routes, OSPF routes are redsitributed into BGP, and BGP routes are redistributed into OSPF.

Why must I clear the OSPF process for the lower cost BGP routes to return? Shouldn't this be dynamic? If so, is there somethign that can be added to the configuration?

----------------------------

Firewall OSPF config:

router ospf 10

network 10.0.2.0 255.255.255.0 area 10.0.0.0

network 10.1.0.0 255.255.248.0 area 0

log-adj-changes

redistribute static metric 220 subnets route-map StaticRedistVPN

route-map StaticRedistVPN permit 8

match metric 220

route outside 10.2.0.0 255.255.248.0 209.252.39.49 220

route outside 10.3.0.0 255.255.248.0 209.252.39.49 220

----------------------------

Router OSPF config:

router ospf 10

log-adjacency-changes

redistribute bgp 65002 subnets

network 10.1.0.0 0.0.7.255 area 0

network 192.168.1.0 0.0.0.255 area 0

network 192.168.252.0 0.0.0.255 area 0

----------------------------

Router BGP config:

router bgp 65002

no synchronization

bgp log-neighbor-changes

bgp redistribute-internal

redistribute ospf 10 metric 200 match internal external 1

neighbor 10.1.1.111 remote-as 65002

neighbor 10.1.1.111 default-originate

neighbor 10.1.1.111 version 4

neighbor 10.1.1.111 soft-reconfiguration inbound

distance bgp 120 120 120

no auto-summary

cjw

Jon Marshall · ‎03-03-2010

cjw wrote:

When the WAN link comes back up the higher OSPF route is NOT dynamically deselected in favor of the BGP route. Instead, we must clear the OSPF process on the WAN routers.

So that every location knows all the routes, OSPF routes are redsitributed into BGP, and BGP routes are redistributed into OSPF.

Why must I clear the OSPF process for the lower cost BGP routes to return? Shouldn't this be dynamic? If so, is there somethign that can be added to the configuration?

----------------------------

Router BGP config:

router bgp 65002

no synchronization

bgp log-neighbor-changes

bgp redistribute-internal

redistribute ospf 10 metric 200 match internal external 1

neighbor 10.1.1.111 remote-as 65002

neighbor 10.1.1.111 default-originate

neighbor 10.1.1.111 version 4

neighbor 10.1.1.111 soft-reconfiguration inbound

distance bgp 120 120 120

no auto-summary

cjw

It's not entirely clear what your topology is but is the config above from your WAN router ? If so what is the line "distance bgp 120 120 120" meant to be doing because AD 120 is higher than OSPF AD 110 so that might explain why the OSPF routes are not getting deselected.

I say might because as i say it's not clear what your topology is.

Jon