@JoeAndreini wrote: I think you are making this harder than it needs to be... I would do the following: 1) configure the new ports on the switch in your VLAN and wire it to the new ports on the firewalls 2) just before your maintenance window, configure the new firewall ports and remove the subinterfaces 3) when the maintenance window begins, apply this candidate configuration 4) once you verify everything is functioning, remove the VLAN from the trunk ports on the switch I would also use exactly these steps for this migration. Specially because I can confirm that was working perfectly fine when I did the opposite (migrate from L3 interfaces to subinterfaces). PaloAlto Firewalls are Zone based firewalls, so the session sync will work during this migration. This is because on a Palo Alto Networks firewall, a session is defined by two uni-directional flows each uniquely identified by a 6-tuple key: source-address, destination-address, source-port, destination-port, protocol, and security-zone. --> nothing about source-interfaces 😉
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