Chapter 18. Monitoring Your Network

Wouldn't it be a lovely world if once you got your network set up and running correctly, you could sit back and relax? Unfortunately, such a world doesn't exist. For your network to remain a lean, mean, routing machine, at least some oversight is required. You need to be able to monitor your network to ensure that things are in order.

This chapter is dedicated to the basic diagnostic tools and instrumentation commands that are essential to the maintenance of a healthy network. It describes how to check connectivity, monitor activity, and ensure that traffic is flowing at breakneck speeds.

Checking Host-to-Host

You'll probably begin monitoring your network immediately after setting up your protocols. The first thing most people do after configuring their router (or other device) is check to see whether they can send traffic across links to other nodes within the network. This test is where the ping command comes into play. Examine the network topology shown in Figure 18-1.

If you run OSPF across all the links in the network, you'd expect to be able to reach any host from any other host. But how do you know whether things are working correctly?

From the JUNOS command prompt, you can issue the ping command. Log into the router you want to start from and send a ping to an address on the remote host to which you expect a route. For example, in the topology shown in Figure 18-1, you might log into router 1. From there, you want to ensure that you have connectivity ...

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