Network Troubleshooting

Before I start blathering on about card configuration and routing, I'd like to issue a couple of caveats. First, the concepts and techniqes discussed in this chapter are not specific to WebLogic and therefore don't really belong in this book. I'm including them because, in my experience, about half of the time when the users come whining about how "the Web server is down" the actual problem ends up being some sort of network SNAFU which has nothing to do with WebLogic.

Second, this is not a complete treatment of network techniques and concepts. To really do the topic justice you'd need about three volumes of dense technobabble in tiny type. Instead, what I'm hoping to do is identify the handful of problems which cause 80% to 90% of the world's network outages.

Third, the example commands shown below will not necessarily work on your system. The closer you get to the hardware level (and network cards are relatively close), the more variations there are across Unix systems. To the best of my knowledge, the commands shown below exist on all the Unix variations. On the other hand, I know for a fact that the output, the options used, and the syntax all vary to some degree. If a particular command won't work for you as displayed, read your man pages.