FG Firewall Transparent Mode L2 Loops

[ataro]

I have a firewall configured on Transparent mode (two interfaces, inside and outside). Also I have a MGMT interface connected to the same vlan. In this case can it form L2 Loops? What is best practice?

[VinayHM · Accepted solution]

Yes, it is possible if the MGMT interface and the other interfaces are all in the same VLAN and there are no loop prevention mechanisms in place.
Multiple switches or network devices connecting to the same VLAN without spanning tree or loop mitigation can cause Layer 2 loops.

[ataro]

I have defined MGMT as OOB dedicated management, even after this setting it forms L2 loop. Is it the normal behavior when the firewall in L2 / Transparent mode? Further I am unable to define VRF for interfaces in Transparent mode.