I Can't See ARP for VLAN1 On Subnet interface in FTD

[Essa_Rahemi]

I am moving the SVI from switch to FTD for vlan1 and using it sub interface, but i dont see arp entry for vlan1. I noticed this at least for 3 different sites and 6 firewalls. it works for other VLANs except VLAN1.

Any idea why is this the issue ? 

[MHM Cisco World]

Change native of trunk connect to FTD to be other vlan not valn1 and check. 

Issue I think because of native of trunk

MHM

[Essa_Rahemi]

this is what i was thinking too. So i will try to change this in MW. i believe this should resolve the issue. 

[balaji.bandi]

I generally avoid VLAN 1  for security reason. and add native vlan as new vlan.

[wajidhassan]

Hi @Essa_Rahemi 

The missing ARP entries for VLAN1 on FTD subinterfaces can be due to:

• VLAN1 reserved behavior: Some Cisco devices treat VLAN1 differently, sometimes limiting features like ARP on subinterfaces.

• Subinterface configuration: Ensure the VLAN tagging and encapsulation on the subinterface is correctly configured for VLAN1.

• Security policies or inspection: Check if any access control or inspection rules on FTD are blocking ARP or related traffic on VLAN1.

• Software versions: Verify if this is a known issue in your FTD version and consider updating to the latest recommended release.

Review these areas; this should help resolve or narrow down the cause.

Hope this helps.