Quick Thought on OSPF

Where I work, we use a lovely tool called RANCID to track changes made to our routers. We get config diffs for most of our routers every 30 minutes. It makes a great sanity check to be able to see changes like that. I’m now sitting at work, having a very long week dealing with software upgrades in the backbone, dealing with bugs and all 3 Cisco’s TAC locations. Naturally, it involves a lot of troubleshooting, but unfortunately long periods of idling, as well. Idling spent writing blogs, Tweets, commenting on just about everything on Facebook and… spying on provisioning team to see if they have any clue. Well, I be damned. They do!

Say that you are dealing with a DSLAM that is multicast challenged in a way that will break OSPF. Just briefly, enabling IGMP snooping on this device will not forward any multicast frames, unless it observes relevant IGMP membership report. Of course, OSPF doesn’t use IGMP, so it breaks. Furthermore, you have business MPLS customer terminated on this box who runs OSPF in the network. How exactly you solve the problem? Well, old telco hand would say to just use static routes and be over with it. Well, our provisioning guys ain’t old telco hands. They are smart (perhaps I should be worried about it)…

Remember old favorite with CCIE exam authors about OSPF in NBMA networks? Yeah, the one where you have to define neighbors explicitly, so that they use unicast and not multicast? Yeah, the one you probably never used in live production network. Well, I be damned #2!

I just saw one of our smart guys pull just that particular trick to go around our multicast challenged DSLAM! Impressed by the youngsters, I am… :-)

She’s still waiting for me at home and I’m blogging again today. I miss my home. I miss my bed. I miss her…

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