![]() Once you know that, it's trivial to correct the configuration. While it's hard to avoid typos, it's fairly easy to use the debug command for OSPF adjacencies, which will quickly let you know if mismatched parameters are a problem. Quite often, due to fat fingers, non-standard configurations or invalid passwords, deviant parameters will prevent adjacencies from forming. ![]() These include authentication, area ID, mask, hello interval, router dead interval, etc. In order to form an adjacency, OSPF routers need to have quite a few parameters in common. Friends don't let friends do mutual redistribution.Įrror #2: Mismatched neighbor parameters in OSPF In fact, redistribution is almost always a bad decision. The best way to avoid this, of course, is to not do redistribution at all. ![]() Not applying filters at all is usually a significant problem, but managing the filters in a complex and poorly summarized network is such an administrative burden that missing a route here or there is extremely common. When redistributing routing you need to filter the routes properly to avoid routing loops and route feedback. With that in mind, let's move on to the errors. For instance, if you're only supposed to be working on one router, and the problem needs to be corrected on another router, do you have access? Are you allowed to change it? If not, do you have the contact information for someone who can? How can you document the change? And let's not forget. You also need to make sure you have the ability to change lots of routers. If you have to fix a lot of errors, it could take a lot more time than anyone expected. You have to be extremely careful in this situation though, because your "fix" can send a flood of new routes into the network, changing traffic patterns that may not be transparent to the users.Īnother gotcha to be thinking about when troubleshooting routing errors is how it changes your customer's expectation of the project's scope. This turns the network into a minefield in which routes aren't propagated as anticipated when you make your changes, so you have to find and remove the "fix," then find and resolve the actual problem. It's fairly common to find situations where a previous administrator committed one of these errors and was unable to resolve it, so they "fixed" it by adding static routes or changing the administrative distance of a protocol. As you probably know, one of the joys of consulting or doing project work as a network reseller, is discovering these little routing errors in customer networks during an install or change window.
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