note to self....

There are several problems that can commonly occur between your host computer and the internet when connecting to the internet using a DHCP to configure host computers on a local area network attached to a cable modem via home router. The setup we are currently discussing here is

• cable modem


• 802.11b/g wireless router


• wireless network card (NIC) in Linux host

These same principles will apply for wired networks and for non-Linux based computers, but any commands specified on the host may differ slightly for either exception. Likewise, the principles will apply for uplink devices other than cable modems (e.g. DSL routers).

There are several things that must happen when the DHCP client configures the NIC on the host computer. DHCP configuratino of the host NIC happens when a network interface is brought up. Typically, network intefaces are brought up either when the computer is powered up, or when the user manually commands it. In this case, we are starting the DHCP configuration of the wireless NIC manually using the Kinternet widget.

The things that must happen during DHCP configuration of the NIC are:

• The host acquires an IP address from the a DHCP server and assigns it to the NIC


• The host acquires a DNS address from the DHCP server and assigns it to the host for use resolving network names


• The host acquires a default gateway address - also known as a default route - which is assigned to the TCP/IP stack on the host and used for all non-local network traffic (i.e. Internet access).

As the host computer NIC is brought up and configured via DHCP, if any of the above operations fails, then the host computer will exhibit behavior which provides a tip-off to what the problem is:

• If no IP address was acquired from the DHCP server, then the network connection has failed - Kintenet will not show an the connection as active, and /sbin/ifconfig will not show an IP address for the wlan0 interface.



• If no DNS server address is provided (or if the DNS is unsuccessfully set on the host), then network names will not be resolved for the host - e.g. web browser requests will time out with "host not found" type errors.



• If no default gateway is provided, or if the default route is not set for the host, then web requests via the browser will be returned immeadiately. Network requests in general will be returned with "network unreachable" errors.

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