This read-only PhysAddress is the MAC destination address the switch places on frames sent toward this next hop. It's operationally important because it's the concrete Layer 2 target for forwarded IP traffic, so verifying it matches the actual next-hop device's interface MAC rules out an ARP-resolution problem as the cause of connectivity issues. For example, after replacing a router with a new NIC, an admin would check this field to confirm the switch has re-learned the new MAC rather than still forwarding to the old, decommissioned address.