>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 co

>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? This is exactly what Cisco Express Forwarding (and similar layer 3 switching technology) does. The adjacency table keeps all of the layer 2 information to be used for fast routing of packets. This was implemented on the CPU back in the day, but now usually done in the switching ASICs. However, you still need layer 3 next-hop information in the routing table (and dynamic routing protocols). The reason being 1. ethernet is one of many layer 2 technologies that IP supports and 2. MAC addresses can change for a particular IP address due to various reasons including hardware replacement and HA.