How traceroute works: TTL, hops and route changes

Traceroute gradually increases the IPv4 TTL or IPv6 Hop Limit and records routers that respond along the way. This reveals part of the route to a destination, not a guaranteed map of every packet’s path.

How traceroute discovers intermediate hops

Traceroute sends probes with increasing TTL or IPv6 Hop Limit values. Routers that expire a probe can return a Time Exceeded message, allowing the sender to observe a sequence of responding hops.

How to read a trace

Run several traces to the same destination and compare where replies change or stop. Missing hops do not automatically indicate packet loss because routers may deprioritise traceroute probes. Focus on whether later hops and the destination remain reachable. For a control trace, use 2ip ping and traceroute.

Why missing hops do not always mean packet loss

Technical reference: RFC 1812.