Traceroute reports probe replies, not a complete map of forwarding health
Traceroute sends probes with increasing TTL values to discover where packets expire and which systems report that expiration. An IPv4 router forwarding a packet decrements its TTL; when it expires, an ICMP Time Exceeded response normally identifies a responding hop. A traditional UDP trace finishes when the destination reports an unused port. The output is a series of observations about probes and replies, not a guaranteed inventory of every forwarding device. ...