FHRP Communication Between Redundant Routers

When FHRP Protocols operates between two L3 devices, communication takes place over the L2 connection between those routers. That L2 connection can be:

  • A direct L2 link between the two (or more) routing devices
  • An L2 link via one (or more) L2 switches that connect the two routing devices

https://networklessons.com/cisco/ccnp-encor/cisco-campus-network-design-basics/