You'll probably begin monitoring your network immediately after setting up your protocols. The first thing most people do after configuring their device is check to see whether they can send traffic across links to other nodes within the network. This initial test is where the ping command comes into play. Examine the network topology shown in Figure 8-1.
If you were to run the OSPF routing protocol across all the links in the network, you'd expect to be able to reach any host from any other host. You still need to verify if things are working correctly, however.
From the Junos OS command prompt, you can issue the ping command. Log in to the device you want to start from and send a ping to an address on the remote host; that is, to the address you expect to have a path to through the network. For example, in the topology shown in Figure 8-1, you might log in to router1. From there, you want to ensure that you have connectivity to router7. So you pick any network address on router7 (any of the interface addresses, or even the loopback address will work) and issue a ping command:
user@router1> ping 10.0.24.2 PING 10.0.24.2: 56 data bytes 64 bytes from 10.0.24.2: icmp_seq=0 ttl=62 time=0.520 ms 64 bytes from 10.0.24.2: icmp_seq=1 ttl=62 time=0.417 ms 64 bytes from 10.0.24.2: icmp_seq=2 ttl=62 time=0.497 ms 64 bytes from 10.0.24.2: icmp_seq=3 ttl=62 time=0.424 ms 64 bytes from 10.0.24.2: icmp_seq=4 ttl=62 time=0.501 ms ^C --- 10.0.24.2 ping statistics --- 5 packets ...