Routers are compatible with LANs and WANs. They can connect different types of networks, so they can handle a number of interface types. To make an interface available, it must:
be configured with at least one IP address: Use interface configuration commands for the ip address Address_IPMask_Subnet and the ipv6 address Address_IP_v6/Prefix.
be enabled: By default, LAN and WAN interfaces are not enabled (i.e., they are shut down). To enable an interface, it needs to be activated using the command no shutdown. This results in the interface being powered up. The interface must also be connected to another device (a concentrator, a switch or another router) to enable the physical layer.
have a description: The interface can optionally be configured to have a short description of a maximum of 240 characters. It is recommended to configure a description on each interface. On production networks, the advantages of having interface descriptions soon become clear because they’re very useful for troubleshooting and identifying a connection and third-party details.
Configure VPN Router
Configure the VPN router as follows:
VPNRouter(config)# interface GigabitEthernet0/0 VPNRouter(config-if)# ip address 192.168.110.254 255.255.255.0 VPNRouter(config-if)# ipv6 address 2001:db8:acad:110::254/64 VPNRouter(config-if)# description VPN subnet link VPNRouter(config-if)# no shutdown VPNRouter(config-if)# exit VPNRouter(config)# interface Serial0/1/1 VPNRouter(config-if)# ip address 10.0.0.2 255.255.255.0 VPNRouter(config-if)# ipv6 address 2001:db8:acad:1001::2/64 VPNRouter(config-if)# description VPNRouter-TBRouter link VPNRouter(config-if)# no shutdown VPNRouter(config-if)# exit
Here’s a little demo video to explain this configuration:
Configure the Loopback Address for Your Router
Another common configuration for Cisco IOS routers is to enable a loopback interface. A loopback interface is a logical interface that is internal to the router. It’s not assigned to any physical ports and can never be connected to another device. It’s considered to be a software interface that is automatically placed in an “up” (active) state while the router is operating.
The loopback interface is useful when testing and managing a Cisco IOS device, because it guarantees that at least one interface is always available. You’ll often use a loopback interface to simulate the internet. The loopback interface is enabled and assigned as follows:
VPNRouter(config)# interface loopback 0 VPNRouter(config)# %LINK-5-CHANGED: Interface Loopback0, changed state to up %LINEPROTO-5-UPDOWN: Line protocol on Interface Loopback0, changed state to up VPNRouter(config-if)# ip address 192.168.200.2 255.255.255.0 VPNRouter(config-if)# exit
Here’s another video showing you how to perform this configuration:
Let's Recap!
In this chapter, you’ve seen:
how to perform basic security configuration on the router (host name, password for privileged EXEC mode, SSH access, password encryption, authorization notice, and non-volatile memory configuration).
how to configure router interfaces (IPv4 address, IPv6 address and description).
how to configure a loopback interface to simulate the internet.
Now that you know how to configure the basic parameters of a router, you’re going to tackle routing configuration!
