A trace returns a list of hops as a packet is routed through a network. The form of the command depends on where the command is issued. When performing the trace from a Windows computer, use tracert. When performing the trace from a router Command Line Interface - CLI, use traceroute.
Ping and Trace
Ping and trace can be used together to detect a problem.
Let's assume that a successful connection has been established between Host 1 and Router A, as shown in the figure.
Next, let's assume that Host 1 pings Host 2 using this command.
C:>ping 172.17.2.3
The ping command returns this result:
Pinging 172.17.2.3 with 32 bytes of data:
Request timed out.
Request timed out.
Request timed out.
Request timed out.
Ping statistics for 172.17.2.3:
Packets: Sent = 4, Received = 0, Lost = 4 (100% loss)
The ping test failed.
This is a test of communication beyond the local network to a remote device. Because the local gateway responded but the host beyond did not, the problem appears to be somewhere beyond the local network. A next step is to isolate the problem to a particular network beyond the local network. The trace commands can show the path of the last successful communication.
Trace to a Remote Host
Like ping commands, trace commands are entered in the command line and take an IP address as the argument.
Assuming that the command will be issued from a Windows computer, we use the tracert form:
C:>tracert 172.17.2.3
The only successful response was from the gateway on Router A. If a Trace requests to the next hop timed out, meaning that the next hop did not respond. The trace results indicate that the failure is therefore in the internetwork beyond the LAN.
If there is a conflicting result, the default gateway-192.168.1.1- responds, indicating that there is communication between Host1 and the gateway. On the other hand, the gateway does not appear to be responding to traceroute.
One explanation is that the local host is not configured properly; check the gateway IP address on the host. To examine the gateway IP address, use the ipconfig command line.
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