How Traceroute can know domain name of Hops?

Question

I'm studying the ICMP protocol and the tool traceroute. I don't understand how can traceroute look up the domain names of Hops if in the ICMP datagram only the IPs can be found. How does it work?

Thank you!

Answer 1

It's called reverse DNS, and is basically the opposite of a domain-to-IP lookup.