ARP (Address Resolution Protocol) explained


I’d like to know how an ARP request between hosts that are physically located in two separate branch offices (so separated by a WAN link) but belong to the same VLAN gets delivered.

Host A → Switch A → Router A → ISP → Router B → Switch B → Host B

Both host A and host B are in VLAN 99. When host A sends an ARP request for host B’s MAC address, that ARP request gets forwarded to Router A. Shouldn’t Router A filter/drop the frame (because routers separate broadcast domains, and an ARP request is a broadcast frame)? But aren’t there real-world topologies where the same VLAN is configured in different branch offices, meaning there is at least one router between the hosts that belong to the same VLAN? So that tells me this should work, but how?

Can someone please explain this to me?

Thanks, and have a nice weekend.