Week 2 of BSCI Studies…OSPF is a LOT to Digest!
I’m starting week 2 of my BSCI studies as well as the very beginnings of my CCIE studies. So far I’m about halfway through my first read of Routing TCP/IP vol. 1 and eagerly awaiting the arrival of my BSCI lab portfolio. I’ve done all my initial reading and study of EIGRP and done a few small labs on it. I will obviously revisit it again later on before I take the BSCI. Right now I’m working on getting a feel for the OSPF topics and boy, is there ever a lot to learn! The scope of OSPF that the CCNA covers is absolutely tiny when compared to the depth of configuration that there is to learn for CCNP and CCIE. I think it comes down to this…OSPF gives you granular control of almost every aspect of how routes are chosen and how the protocol works in ways that few other IRP’s do.
I’m already seeing the sacrifices that will have to be made in order to study for my CCIE. I’ve quit my company’s softball team because that would eat up at least 4 hours of study time per week that I just don’t feel like I can give up. My children are already dreading hearing that Mommy has to go study, but luckily my husband is holding down the home front. I know I will have to balance my studies with family to some extent, so it looks like the biggest sacrifice that’s going to have to be made will be any time for myself that does not involve studying will just have to go. I will either be working, studying, or spending time with the little ones for the next year or so…not much else. Still, in my mind the prize is worth the price.
One of the things that I’ve found surprising, probably since I’ve never worked in an environment with more than one IRP running is that a router will prefer a route with a longer prefix regardless of the Administrative Distance of the protocol it learned the route from. I also find it ridiculous that IGRP has a lower AD than OSPF. Here’s my list of AD’s to remember:
0 - Directly Connected Network or Static Route using an exit interface instead of next hop address
1 - Static Route using next hop address
5 - EIGRP Summary Route
20 - External BGP
99 - Internal EIGRP
100 - IGRP
110 - OSPF
120 - RIP
170 - External EIGRP
200 - Internal BGP
255 - Unknown Network
Which leads me to wonder if there was any logic at all applied when assigning these Administrative Distances? Right now I feel like my own AD as far as understanding all this must be pretty high up there…maybe only a bit lower than an Unknown Network. :( Time to get back to studying!
AD are something you need to know for written tests, and thats about it. In lab or even real situations, as long as you understand what an AD is, and take it into consideration when working with multiple routing protocols over the same domain (which honestly isn’t that often), you can get by fine. Even if you don’t remember the AD of say EIGRP, but you want OSPF routes instead, just let the EIGRP install, take a look a the AD of the route, and configure OSPF accordingly. The convergence speed is fast enough to not really waste much time.
That said, the reason something like EX-BGP is a lower AD (which you would think OSPF or something would be trusted more right?), is because EX-BGP is something that was ‘forced’ in manually. Meaning if a route is learning it, it probably isn’t automatic like OSPF, and was specifically designed. Why IGRP > OSPF I have no idea lol