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# Interface Configuration for IP

After setting up your hardware as explained in the previous chapter, you have to make these devices known to the kernel networking software. A couple of commands are used to configure the network interfaces, and initialize the routing table. These tasks are usually performed from the rc.inet1 script each time the system is booted. The basic tools for this are called ifconfig (where ``if'' stands for interface), and route.

ifconfig is used to make an interface accessible to the kernel networking layer. This involves the assignment of an IP-address and other parameters, and activating the interface, also known as ``taking up.'' Being active here means that the kernel will send and receive IP-datagrams through the interface. The simplest way to invoking it is

               ifconfig interface ip-address

which assigns ip-address to interface and activates it. All other parameters are set to default values. For instance, the default subnet mask is derived from the network class of the IP-address, such as 255.255.0.0 for a class-B address. ifconfig is described in detail at the end of this chapter.

route allows you to add or remove routes from the kernel routing table. It can be invoked as

               route [add|del] target

where the add and del arguments determine whether to add or delete the route to target.

- The Loopback Interface
- Ethernet Interfaces
- Routing through a Gateway
- Configuring a Gateway
- The PLIP Interface
- The SLIP and PPP Interface
- The Dummy Interface