ospf1 - Introducing OSPF...

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Introducing OSPF Peter J. Welcher Introduction The OSPF routing protocol is playing an increasingly important role in modern networks. It is a multi-vendor standard. We'll take a look at OSPF basics in this article. While I and a number of people are fans of Cisco's EIGRP for its simplicity and ease-of-use, lately I'm seeing more use of OSPF. This may be due to networking staffs having increasing levels of sophistication. Or it may be that folks are looking at to the next generation of hardware, and thinking that OSPF is something you'll find in any worthwhile Layer 3 switch ("fast router"). After all, who'd want to buy a fast Layer 3 switch that only routes using RIP or RIPv2, with their slow convergence? That's basically the "it's a standard" argument -- you do OSPF if you anticipate using mixed vendor equipment in your network, or if you at least want to maintain that possibility. Running OSPF so your routers can exchange information with NT servers is probably not a Good Thing. I personally don't want servers sending routing information to my "official routing protocol", since I've seen too many servers with duplicate IP addresses or other oddities. If a server administrator goofs and duplicates the server farm subnet on some workgroup server somewhere else, and it advertises it into your network, you're in for a serious outage! If your group controls the servers, or if NT servers are acting as low-end routers at remote sites, well, then there's a reason to run OSPF. I'll just mention in passing here that OSPF has an authentication feature that allows you to easily exclude any "unofficial" routers from your OSPF Autonomous System ("group of consenting routers"). I don't think I'm revealing any deep dark secret if I tell you that you need to know OSPF well for the CCIE test and for recertification. The general rule of thumb is, if it's a major protocol or feature, used at a lot of sites, it's probably in the test. (There's also minor stuff, presumably to see if you can Read The Fine Manual and get it working). Pros and Cons of OSPF The chief reasons for using OSPF are fast convergence and the fact that it's an IETF standard. It does minimize bandwidth consumed by routing information, using low bandwidth wisely, and it does take WAN link bandwidth into account, preferring high bandwidth paths. The drawbacks are the area structure and design aspects of OSPF, which we'll look at below. This Introducing OSPF http://www.netcraftsmen.net/welcher/papers/ospf1.htm 1 of 6 1/6/03 9:06 AM
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means you have to plan for how your network is going to grow when doing an OSPF design -- and some people would say that's a good thing. The protocol is mildly complex, so there is perhaps a steeper learning curve than EIGRP. Finally, configuring OSPF is a little more work than configuring EIGRP. OSPF Design
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ospf1 - Introducing OSPF...

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