route print command show almost all On-link gateway - networking

Question

Trying to learn about routing tables, when preforming route print on cmd window I get this result on the IPv4 table:
===========================================================================
Active Routes:
Network Destination Netmask Gateway Interface Metric
0.0.0.0 0.0.0.0 10.0.0.138 10.0.0.9 50
10.0.0.0 255.255.255.0 On-link 10.0.0.9 306
10.0.0.9 255.255.255.255 On-link 10.0.0.9 306
10.0.0.255 255.255.255.255 On-link 10.0.0.9 306
127.0.0.0 255.0.0.0 On-link 127.0.0.1 331
127.0.0.1 255.255.255.255 On-link 127.0.0.1 331
127.255.255.255 255.255.255.255 On-link 127.0.0.1 331
224.0.0.0 240.0.0.0 On-link 127.0.0.1 331
224.0.0.0 240.0.0.0 On-link 10.0.0.9 306
255.255.255.255 255.255.255.255 On-link 127.0.0.1 331
255.255.255.255 255.255.255.255 On-link 10.0.0.9 306
===========================================================================
From my understanding, the Network Destination and Netmask combine show the Network ID, and Gateway is the "next hop" meaning it is the address where addresses from Network ID can get to the internet, via the Interface on the right.
This table is different from other I seen on line, and almost all the gateways are On-link. From a simple google search, I found those On-link mean addresses reachable locally (my router's address?) so On-link=10.0.0.138 in this example? And since network ID is all 0.0.0.0 that means the only routing available on my system is going to 10.0.0.138 through 10.0.0.9? If so why I need the other rows? If I'm wrong I would love to know better.
Thanks.

Answer 1

"on-link" doesn't equal 10.0.0.138. It means that the destination network is directly attached to the interface - meaning traffic that matches this route entry will trigger an ARP request that should be sent from this link to resolve the destination IP directly (not the gateway 10.0.0.138).
This is also called "glean adjacency".
The 10.0.0.9 route instructs packets with destination IP 10.0.0.9 to be sent to the CPU (AKA punt adjacency).
127.0.0.0/24 network is for internal communication within the machine.
224.0.0.0/4 is for multicast traffic.