Describe how traceroute checks the routing between different networks.

What will be an ideal response?

The traceroute diagnostic tool is primarily used to check the routing between different networks. To achieve this task, traceroute sends packets with an increasing TTL value to the destination host, whereby three packets of each value are sent.
Traceroute also uses UDP packets, which are called datagrams.
First, three datagrams with a TTL=1 are sent to the host, then three packets with a TTL=2, and so on. Every time a datagram passes through a router, its TTL is reduced by one.
When the TTL reaches zero (0), the datagram is discarded and a message is sent to the sender. Because the TTL is increased by one every three packets, traceroute can collect information about every router on the way to the destination host.
You normally include a hostname with the traceroute command, but it is also possible to use an IP address instead of the hostname.