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Summary:
After restoring a configuration file on a FortiGate that uses multiple VLANs, users report no inter-VLAN communication, even though the policies appear to be configured correctly.
Symptoms:
- Devices within the same VLAN can communicate without issue.
- There is no ping response or traffic between different VLANs.
- Inter-VLAN firewall policies are configured correctly.
- There are no traffic denial logs.
Probable cause:
After restoring a configuration, especially from a different FortiGate model or between different firmware versions,
VLAN interfaces may be restored as 'zones' or lose route/ARP associations without any visible errors.
VLAN interfaces may also be associated with the wrong physical interface after the restore, or policies may depend on zones that are no longer active.
Solution:
- Verify the restored VLAN interfaces: Check that the VLANs are correctly associated with the corresponding physical interface.
show system interface
- Validate the associated routes: Ensure there are valid static or dynamic routes that allow communication between networks.
get router info routing-table all
- Test connectivity directly from FortiGate:
execute ping-options source [IP_VLAN_A]
execute ping [IP_VLAN_B]
- Delete and recreate zones (if applicable):
If the policies reference zones, verify that the zones still correctly group the necessary interfaces.
If not, delete and recreate the zones from scratch.
- Verify the ARP and MAC Address Table:
diagnose ip arp list
diagnose switch mac-address list
- Review traffic with debug flow:
diagnose debug enable
diagnose debug flow filter addr [IP]
diagnose debug flow show function-name enable
diagnose debug flow trace start 100
Additional Notes:
- This issue typically occurs during migrations between FortiGate models or restores between different firmware versions.
- Whenever possible, perform a line-by-line review of the '.conf' file before applying it to production.
- For converting configuration, use Forticonverter.
Related document:
VLAN - FortiGate 7.6.3 administration guide
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