This read-only PhysAddress is the MAC destination address used to forward IPX traffic for this sub-network forwarding entry. It's the concrete Layer 2 target hardware writes onto frames for that network-level route, so an admin can verify it matches the actual next-hop router or gateway address for that IPX network. For example, if an entire IPX network becomes unreachable, checking this MAC against the known gateway's address helps confirm whether stale address resolution is the cause.