Router - a device that is good at computing routing tables, an L3 device.

Routing Table

  • A NIC with one IP naturally has two routes and they cannot be changed. 192.168.1.1/24
    • Itself. Local route / Host route: 192.168.1.1/32
    • The whole subnet. Direct route / Connect route: 192.168.1.0/24
  • You can add as many static routes as you want.
    • 172.10.10.10/24 -> 192.168.1.2
    • 2.2.2.2/26 -> 192.168.1.9
    • …
  • Default route - only one gateway.
    • 0.0.0.0/0 -> 192.168.1.10
  • More specific routes take precedence.
  • BGPv4