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Any packets forwarded to the internet will pass through different routers. For each packet, one path to reach the destination will be selected. The FortiOS 'traceroute' command can provide some information about the likely path.
Examples:
In the traceroute output, the IP address of each hop and the response time are visible if a response was received.
execute traceroute 1.1.1.1
traceroute to 1.1.1.1 (1.1.1.1), 32 hops max, 3 probe packets per hop, 72 byte packets
1 10.31.12.1 2.678 ms 2.544 ms 1.979 ms
2 154.11.15.107 2.331 ms 3.235 ms 2.971 ms
3 154.11.15.73 <qubcpqajdr02.bb.telus.com> 4.216 ms 19.313 ms 23.510 ms
4 1.1.1.1 <one.one.one.one> 3.252 ms 2.992 ms 2.945 ms
Each '*' in the traceroute output represents one ICMP probe that received no response.
If there are three stars, then all three ICMP probes that were sent out had received no responses.
If the same output ('***') appears each time traceroute is run, the hop is not responding with ICMP messages. This may be expected or may be the result of a temporary overload, and does not by itself indicate an issue, particularly if routers later in the sequence do respond.
execute traceroute harvard.edu
traceroute to harvard.edu (151.101.194.133), 32 hops max, 3 probe packets per hop, 72 byte packets
1 10.31.12.1 2.966 ms 2.809 ms 2.979 ms
2 154.11.6.192 15.983 ms 19.186 ms 14.981 ms
3 * * *
4 151.101.194.133 <harvard.edu> 16.532 ms 16.722 ms 14.887 ms
In the third traceroute, responses are received until step 2, but nothing is received afterwards. This may indicate a routing issue at 154.11.15.111 or one later in the path. It may also indicate a large sequence of routers that are configured not to respond with ICMP messages.
execute traceroute 2.2.2.2
traceroute to 2.2.2.2 (2.2.2.2), 32 hops max, 3 probe packets per hop, 72 byte packets
1 10.31.12.1 2.863 ms 2.883 ms 2.988 ms
2 154.11.15.111 7.361 ms 14.821 ms 10.321 ms
3 * * *
4 * * *
5 * * *
6 * * *
If a traceroute returns '!H', this indicates that the router returned an ICMP 'destination unreachable' message. Typically, this occurs when the remote router has no valid route to forward the traffic further.
execute traceroute 1.1.1.1
traceroute to 1.1.1.1 (1.1.1.1), 32 hops max, 3 probe packets per hop, 84 byte packets
1 10.10.10.1 63.376 ms !H 1089.821 ms !H 2999.721 ms !H
If IPv6 is enabled in the FortiGate's feature visibility settings and an IPv6 address is configured on an interface, it is possible to traceroute IPv6 destination addresses using the command below:
execute tracert6 ?
arg please input args
execute tracert6 2001:db8:a0b:13e0::6
tracert6 to 2001:db8:a0b:13e0::6 (2001:db8:a0b:13e0::6), 30 hops max, 40/8 byte payload/paddata
1 * * *
2 * * *
Related article:
Troubleshooting Tip: Using traceroute options from FortiGate CLI
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