In this level, the routers use the time to live (TTL) field. The TTL field is designed to keep packets from getting trapped in infinite loops: each router decreases the TTL value by one, and if it ever reaches zero, it stops forwarding the packet and returns an error message instead.
We have hidden the IP addresses of the routers in this level. Your job is to figure out who they are!
Fun fact: This trick is called "tracerouting", and you can do it for real to see the routers between you and anyone else. Ask a TA to show you how!