I finished reading the OSPF chapter tonight, and I’ll start on the write-up tomorrow. Man, it’s a tougher chapter than I was expecting. I thought I knew OSPF pretty well. I do know it okay, but after reading that chapter, I’m finding that there’s a lot of things that “just worked”, but I didn’t really understand enough of why they worked. Nor would I have known enough to quickly troubleshoot adjacency issues without digging into cisco.com. That said, I’m glad I have the background I do in OSPF. I managed a large-ish OSPF network once upon a time, several areas, multiple transport types, including a project to take 2 large OSPF networks and make them one big monster. But this chapter brought out so many little details.
For instance…I knew the main LSA types, but that’s not the kind of thing you think about every day, so you forget. So I had to review those. And I didn’t know or it never occurred to me that OSPF routers on a point to point link don’t elect DR’s and BDR’s. And the whole thing about OSPF costs needs a major review for me. While I messed with auto-cost reference bandwidth, implementing a reference bandwidth a co-worker came up with so that we could scale to 10Gbps links, I never messed with the actual cost commands where you can override what OSPF would naturally calculate the link to. Summarization/LSA type 3 commands I grasp, but didn’t quite get how they reduce SPF overhead in outlying areas. And so on. A lot of detail to go back through.
IF I’m dilligent and IF I don’t get distracted by oh, you know, LIFE…then I MIGHT be able to have the write-up done by the end of the day Saturday. I think that’s an attainable goal. I expect it will take me 4-6 hours total. And then I think I want to go back and read Cisco’s OSPF design white paper…it’s been 3 years since I read it, and as I recall, it’s pretty solid. Might be good to hit up the fundamentals again, then read this OECG chapter again in light of that.
You know – at the same time, I don’t want to over-obsess about OSPF. I still have BGP, which I pretty much DON’T know, to conquer. It’s a big book, and a major test. The whole test isn’t OSPF. So I know I have more work to do, but I won’t kill myself trying to nail down every single command.