The traceroute page, located at Diagnostics > Traceroute, works like the traceroute command found on many platforms. It sends special packets which, as the name implies, trace a route across the network from the pfSense® host to a remote host. A list of hops between hosts will be displayed, along with response times, as long as the intervening hosts support (or don’t filter) traffic required for traceroute to work.
Host: A hostname or IP address to which the route will be traced.
IP Protocol: The address type to use when a hostname is entered that has both A (IPv4) and AAAA (IPv6) records.
Source Address: The IP address from which the trace will be sent. This is especially important when testing LAN-to-LAN VPN connectivity.
Maximum number of hops: The maximum length of the path to trace. The trace will stop if the path cannot be traced completely after this number of hops.
Reverse Address Lookup: When checked, traceroute will attempt to perform a PTR lookup to locate hostnames for hops along the path. Will slow down the process as it has to wait for DNS replies.
Use ICMP: By default, traceroute uses UDP but that may be blocked by some routers. Check this box to use ICMP instead, which may succeed.
The output will be displayed once the trace is complete. The Stop button may be pressed at any time to see the current output of the trace if it is still running or stalled.