Fortiauthenticator: Troubleshooting with tcpdump
July 16, 2020
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Had a strange issue the other day with a FAC, where it would not send emails to users with their assigned tokens, but would send emails just fine any other time. I wanted to capture all outgoing traffic to see if SMTP messages were really being sent.
Fortiauth has Tcpdump built in, and is very easy to run.
First SSH into the FAC, from there you have some execute options. Below shows the tcpdump options:
tcpdump Examine local network traffic.
tcpdumpfile Same as tcpdump, but write output to a file downloadable via GUI.
If you run ‘exe tcpdump’ it will spit all the traffic to the screen, but if you run ‘exe tcpdumpfile’ it will log the output to a .pcap that is downloadable from the GUI. This gives you the option to open it in Wireshark and analyze.
To download the .pcap open your Fortiauth append /debug to the web address for example: https://10.110.2.60/debug. From here you will be prompted with what you want to debug, and at the bottom is the option to open the “CLI Packet Capture” this gives you the option to download the pcap.
Thats it! Thank you Fortinet.