Connectivity bug related to "Enable Static ARP entries" Option in the DHCP section

[fionnb]

I struggled with a problem for some time where one of my vLans constantly lost WAN connectivity after varying periods of time. A reboot fixed the problem but it always came back, sometimes after two hours, sometimes after two days. After trying around a lot I finally found out that disabling the static ARP entries option for DHCP made the problem go away. Since all clients on that vLAN do have static leases with static arp enabled and sometimes it works and sometimes not I suspect there is a bug there to be fixed.

Problem occurred on 17.1 as well as 17.7 and 17.7.1

Steps to reproduce my use case:

• Create a trunked interface with at least 2 tagged vLans on it (maybe a regular interfaces are sufficient but I do not have a spare one to test with)
• at least one vLAN interface (A) gets a default WAN route so devices on it have WAN access
• at least one vLAN interface (B)
  • does not get a default WAN route
  • has at least one client with static DHCP lease, static ARP and its own WAN route
  • has "Enable Static ARP entries" Option enabled globally for that interface

You may find a more detailed description of the proceedings in this opnsense forum thread.
Now sit and wait and (hopefully) watch the client on B lose all connectivity after some time. It can not even be reached from the router then (see forum thread).

[AdSchellevis]

Timeout

[JOduMonT]

My comment is just to be sure nobody open an issue about this because he/she also assume or expect a different result:

as @AdSchellevis mentioned there

Warning: This option persists even if DHCP server is disabled. Only the machines listed below will be able to communicate with the firewall on this NIC.