OSPF not advertising learned routes

[dennylester]

We are in process of migrating our entire MPLS connected network from one provider to another. In our datacenter, we have a link to both MPLS networks and will be the gateway between the two until we're fully migrated. We run OSPF between us and each provider and they redistribute into BGP to run across their backbones.  

We just migrated two remote sites to the new provider and realized our leaned routes from one MPLS network are not being advertised out to the other. These learned routes are coming in as E2.

router ospf 1
log-adjacency-changes
redistribute static subnets route-map RedistStaticRoutes
passive-interface default
no passive-interface Serial0/1/0:1
no passive-interface Multilink1
network 172.20.xx.xx 0.0.0.3 area 0
network 172.31.xx.xx 0.0.0.3 area 0
default-information originate always

Any suggestions?

Denny

[manish arora · Accepted solution]

Not sure about how your topology is but if you are using OSPF between CE and PE  and the PE is the one who is redistributing routes learned from CE to its BGP VPN VRF , then in order to avoid loops,

PE routes disregard OSPF routes received from a CE router if the routes are advertised by:

• A type 3 LSA with the most-significant bit set in the LSA options field.
• A type 5 LSA that has a tag value equal to the VPN route tag associated with the OSPF VRF on that PE router.

Manish Arora

[dennylester]

Hi Manish,

Your assumption is correct, it's the PE distributing the OSPF routes in/out of BGP.

Given both problems you mention

• A type 3 LSA with the most-significant bit set in the LSA options field.
• A type 5 LSA that has a tag value equal to the VPN route tag associated with the OSPF VRF on that PE router.

What would you suggest for an acceptable workaround? Would two OSPF processes and redistributing routes between them address this?

Thank you,

Denny

[manish arora]

Hi Denny,

I think , since the redistriburtion is happening at the ISP PE , they might not redistributing the external routes from CE ospf process. I would say, give your ISP a call and have them check the redistribution before moving on to some other solution.

Manish

[dennylester]

Luckily Sprint has this great tool (Compass) that allows me to see the router config they used on my circuits. I confirmed they were redistributing Internal and External 1&2 routes into BGP.

I broke my OSPF configuration into two processes and redistributed between the two. My routes are now coming across the links.

Thank you,

Denny

[manish arora]

Perfect Denny !  I learned a little more today from your solution

Thanks

Manish