> Couldn't you simply put the next hop's MAC address (instead of IP address) into the routing table and be able to route packets just as well, with a lot less complexity?
One reason why using an IP is still important is the IP can move to a different router, so the MAC for that IP can change. Eg if a hardware swapout was performed, or the network admin manually moved the IP, or some HA system that dynamically moves IPs to other routers (and isn’t VRRP, which uses a virtual MAC).
Usability: it’s a lot easier imo to read a routing table with IP next hop than MAC as you don’t have to remember what MAC every machine is. The IP also conveys visually which port the traffic is (probably) going out. Eg
Port 1 - 192.168.1.0/24
Port 2 - 192.168.2.0/24
If my next hop for 1.1.1.1 is via 192.168.2.254 I know immediately it’s going out port 2. If it was a MAC I’d have no clue unless I memorised all MACs in my networks.
One reason why using an IP is still important is the IP can move to a different router, so the MAC for that IP can change. Eg if a hardware swapout was performed, or the network admin manually moved the IP, or some HA system that dynamically moves IPs to other routers (and isn’t VRRP, which uses a virtual MAC).
Usability: it’s a lot easier imo to read a routing table with IP next hop than MAC as you don’t have to remember what MAC every machine is. The IP also conveys visually which port the traffic is (probably) going out. Eg Port 1 - 192.168.1.0/24 Port 2 - 192.168.2.0/24
If my next hop for 1.1.1.1 is via 192.168.2.254 I know immediately it’s going out port 2. If it was a MAC I’d have no clue unless I memorised all MACs in my networks.