Traceroute (Why, How, Alternatives)

Why use the traceroute?

When Server/Network administrator troubleshoots, use the traceroute command to find information about the network hops.

• Trace the route
• Trace the hops from starting point to the destination
• Troubleshoot by catching the breaking hop where the packet has been dropped

How does traceroute work?

The traceroute works by sending a series of packets with incrementally increasing Time-To-Live (TTL) values and monitoring the ICMP error messages returned by each router along the path.

1. The source host sends an ICMP packet with a TTL value of 1 to the destination host.
2. The first router in the path decrements the TTL value of the packet by 1 and forwards it to the next router. If the TTL value reaches 0, the router discards the packet and sends an ICMP “Time Exceeded” message back to the source host.
3. The source host receives the “Time Exceeded” message and records the IP address of the router that sent it.
4. The source host sends another ICMP packet with a TTL value of 2 to the destination host.
5. The second router in the path decrements the TTL value of the packet by 1 and forwards it to the next router. If the TTL value reaches 0, the router discards the packet and sends an ICMP “Time Exceeded” message back to the source host.