TCP/IP Configuration in A Wireless Network (Client in Infrastructure Mode, or Ad-hoc Mode)#

Assigning an IP address to your wireless interface is independent of the 802.11 network configuration and uses the same utilities or daemons as a wired network. The main issue is whether your TCP/IP configuration is dynamically assigned, or statically configured. A static TCP/IP configuration can be applied regardless of the state of your wireless network connection. The wireless network could be active, or it could be unavailable until later. A dynamically assigned TCP/IP configuration (via the DHCP protocol) requires that the wireless network configuration be active, so that it can reach the DHCP server somewhere on the network. This is typically applied in a network that is centrally administered (using Infrastructure Mode with a WAP).

The most common use case is that you are a client using a Wireless Access Point to connect to the network. In this kind of network, there should be a DHCP server available. After the 802.11 network status is active, you just need to start dhcp.client to complete your TCP/IP configuration

• dhcp.client -iral0

As an alternative, you could use lsm-autoip.so. AutoIP is a special case in that it negotiates with its peers on the network as they become available. You do not need to wait until the network link is active to launch it. AutoIP will assign your network interface an IP address, and resolve any IP address conflicts with your network peers as they are discovered by either your host or the peer changing its current IP address. You will be able to use this IP address once the wireless network is active. Please see the AutoIP documentation for more information.

The last configuration option is a static configuration, which does not change without intervention from the user. An example of a static configuration is

• ifconfig ral0 10.0.0.5 (Where 10.0.0.5 is your wireless interface IP address)
• route add default 10.0.0.1 (Where 10.0.0.1 is your network gateway)

• cat /etc/resolv.conf

		domain company.com 
		nameserver 10.0.0.2 
		nameserver 10.0.0.3 

The other use case is an ad-hoc network. This network mode will typically be made up of a number of standalone peers with no central services. Since there is no central server it is likely that DHCP services will not be available.

If there are Windows or Apple systems on your ad-hoc network, they will enable the AutoIP protocol to assign an IP address. By using AutoIP, you will avoid IP address conflicts (two or more hosts using the same IP address) and avoid having to configure a new IP manually. Your IP address will be automatically configured, and you will be able to exchange TCP/IP packets with your peers.

If you are using a static configuration in an ad-hoc network, you will have the added task of deciding what IP address will be used on each system, making sure that there is no conflicts, and that all the IP addresses assigned are on the same subnet so that the systems can communicate.