8.6 Summary

8.6 Summary

Traceroute is an indispensable tool when working with a TCP/IP network. Its operation is simple: send UDP datagrams starting with a TTL of 1, increasing the TTL by 1, to locate each router in the path . An ICMP time exceeded is returned by each router when it discards the UDP datagram, and an ICMP port unreachable is generated by the final destination.

We ran examples of traceroute on both LANs and WANs, and used it to examine IP source routing. We used loose source routing to see if the route to a destination is the same as the return route from that destination.