tracepath — Path and MTU tracing

Linux / Network and Firewall / tracepath.html

Traces the route to a host and reports the MTU of each hop without special privileges.

Basic Information

What is this command?

tracepath raises the TTL step by step and records each hop and the path MTU.

It works without raw socket privileges, which makes PMTU problems easy to spot.

What problems does it solve?

• List the routers between you and a destination.
• Check per-hop MTU to find fragmentation problems.
• Spot asymmetric paths or silent hops.
• Inspect routes across VPN or tunnel links.

Key features

Basic trace

Passing a destination traces the route to it.

• When to use: When the path breaks somewhere.
• What you get: Hops and round-trip times are printed.
• Limitations: Hops that block ICMP appear without answers.

MTU check

Each hop line includes the discovered pmtu value.

• When to use: When only large packets fail.
• What you get: You learn the smallest MTU along the path.
• Limitations: Blocked ICMP can make the value unreliable.

Limit output

You can limit the hop count and the number of probes.

• When to use: When you want shorter output.
• What you get: Tracing stops at the chosen limits.
• Limitations: Too small a value may never reach the target.

Installation and usage

Check whether it is installed

tracepath --version

sudo apt install iputils-tracepath

Real-world examples

Basic trace

Trace the path to a host.

tracepath example.com

Limit hops

Trace at most ten hops.

tracepath -m 10 example.com

Force IPv4

Trace over IPv4 only.

tracepath -4 example.com