Router Configuration

---

• routers serve both to:
  • link physically remote networks
  • subdivide autonomous IP networks into multiple subnets
• router placement is driven by IP networks and subnets:
  • hosts with addresses in the same subnet or IP network must not be separated by a router
  • conversely, hosts with addresses in different subnets or IP networks must be separated by a router

Example

Typical network configuration.

• edge router/firewall provides access to the internet
• traffic between the local subnets is controlled by a separate internal router

• router appliance is configured locally either via:
  • a serial connection
    • known as a console port
  • or remotely over the network via SSH
    • SSH can be used to communicate with the router via the IP address of any configured interface
    • but since a physical interface can suffer a hardware fault or be temporarily unavailable for a variety of reasons
      • it is best practice to create a virtual interface in the router’s OS and assign it an IP address for use in remotely managing the router
        • known as a loopback interface
        • this is a way of giving the router an internal IP address not connected to any physical network
          • therefore not reliant on a specific network link being available
• next configuration tasks include:
  • Apply an IP configuration to each interface
  • configure one or more routing protocols and/or static routes