CLI Commands for Troubleshooting FortiGate Firewalls

This blog post is a list of common troubleshooting commands I am using on the FortiGate CLI. It is not complete nor very detailled, but provides the basic commands for troubleshooting network related issues that are not resolvable via the GUI. I am not focused on too many memory, process, kernel, etc. details. These must only be used if there are really specific problems. I am more focused on the general troubleshooting stuff. I am using it personally as a cheat sheet / quick reference and will update it from time to time.

Coming from Cisco, everything is “show”. With Fortinet, you have the choice between show | get | diagnose | execute. Not that easy to remember. Likewise the sys | system keyword. It is always “diagnose sys” but “execute system”. 😉

Entering the correct vdom/gobal Config

Remember to enter the correct vdom or global configuration tree before configuring anything:

 

To show the running configuration (such as “show run”), simply type in:

To show the entire running configuration with default values, use:

To omit the “–More–” stops when displaying many lines, you can set the terminal output to the following, which will display all lines at once. This is similar to “terminal length 0” from Cisco. Be careful with it, because this command is persistent. Set it to default after usage!

To find a CLI command within the configuration, you can use the pipe sign “|” with “grep” (similar to “include” on Cisco devices). Note the “-f” flag to show the whole config tree in which the keywords was found, e.g.:

 

General Information

The very basics:

 

After rebooting a fresh device which is already licensed, it takes some time until it is “green” at the dashboard. The following commands can troubleshoot and start the “get license” process. Use the first three to enable debugging and start the process, while the last one disables the debugging again:

 

General Network Troubleshooting

Which is basically ping and traceroute:

 

Routing

 

High Availability

 

Session Table

Display the current active sessions:

 

Sniffer

Sniff packets like tcpdump does. This can be used for investigating connection problems between two hosts. There are no details of the firewall policy decisions. Use the debug flow (next paragraph) for analysis about firewall policies, etc.

with:

verbose:
1: print header of packets
2: print header and data from ip of packets
3: print header and data from ethernet of packets (if available)
4: print header of packets with interface name
5: print header and data from ip of packets with interface name
6: print header and data from ethernet of packets (if available) with intf name
count: number of packets
time-format:
a: UTC time
l: local time

Examples: (Thanks to the comment from Ulrich for the IPv6 example)

Here are two more examples on how to show LLDP or CDP packets in order to reveal the connected layer 2 ports from switches. Kudos to Joachim Schwierzeck.

 

Flow

If you want to see the FortiGate details about a connection, use this kind of debug. E.g., it shows the routing decision and the policy, which allowed the connection.

Example:

 

VPN

To show details about IKE/IPsec connections, use these commands:

To debug IKE/IPsec sessions, use the VPN debug:

To reset a certain VPN connection, use this (Credit):

 

Log

For investigating the log entries (similar to the GUI), use the following filters, etc.:

 

Defaults

Just a reminder for myself:

  • IP: 192.168.1.99
  • Login: admin
  • Password: <blank>

To change the IP address of the mgmt interface (or any other) via the CLI, these commands can be used:

 

Links

27 thoughts on “CLI Commands for Troubleshooting FortiGate Firewalls

  1. Nice Job – good summary of most of the commands you need or routinely use.
    John K. NSE7

      1. Hi ihsan,
        I am not aware of a global history of commands. As far as I know you can only move through your own commands in that current CLI session (arrow up key).

        With the following CLI command you can see how many lines are stored in the history buffer:
        get gui console status

  2. Be careful using this as a sniffer. “Sniff packets like tcpdump does. ” is not a true statement. Fortinet support reports that if you have devices with ASIC offload enabled and you’re running anything in the v5 train, you will not see the entire conversation as you would with tcpdump.

    You must DISABLE ASIC OFFLOAD (see page 10 of http://docs.fortinet.com/uploaded/files/1607/fortigate-hardware-accel-50.pdf). Unfortunately for me, I can’t make live mods to firewall policies for troubleshooting. Disabling auto offload now makes the Fortigate sniffer less useful… 🙁

  3. Great thanks! What is the command on 5.2.x to check file system for errors and repair?
    The following does not work: diagnose system file-system fscheck

    1. Hi Alex,
      try the following:
      diag hardware deviceinfo disk
      diag hardware smartctl -a /dev/sda
      I don’t know if this is exactly what you are searching for. But you’ll get some information about the disks.

  4. Some additional information for sniffing a IPv6 subnet:
    # diagnose sniffer packet any ‘net 2001:db8::/32’ 6 1000 l

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