VXLAN over IPSEC - ARP Table Issue on Inter-VLAN Communication

Hello,

I’ve set up two sites connected via VXLAN over IPSEC, and everything is functioning as expected.

However, I’ve noticed an issue with ARP behavior under specific conditions:

• From Site A, when I connect from another VLAN (e.g., VLAN 30) to a virtual machine in VLAN 10 or VLAN 20 on Site B, I observe a change in the ARP table on the device in Site B.

Example:

• I check the ARP table of PC B20 (a device in VLAN 20 on Site B).
  • The MAC address for 10.112.20.254 (router’s IP) initially shows 00:09:0f:09:00:00 (MAC address of the FortiGate on Site B).
• When I connect from PC A30 (a device in VLAN 30 on Site A) to PC B20, and I re-check the ARP table on PC B20, the MAC address for 10.112.20.254 changes to 00:09:0f:09:02:00 (MAC address of the FortiGate on Site A).

This unexpected behavior raises concerns about network stability and could impact communication.

Has anyone encountered a similar issue, or does anyone have insights on why the ARP entry changes in this way? Could this be related to VXLAN or routing settings?

Thanks in advance for your help!