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Howtos - Handling Problematic Cable and DSL Modems

[edit] Overview

Some cable (and prehaps DSL) modems will enter a diagnostic mode and interfere with the operation of your Internet connection. These modems go into a diagnostic mode and enables a local DHCP server. This DHCP server then interferes with the operation of your Internet connection. This howto includes a workaround for the issue.

[edit] Symptoms

The first symptom that you will notice is the lack of an Internet connection! Check the /var/log/messages file for the following pattern:

some date testbox dhclient: DHCPACK from 192.168.100.1
some date testobx dhclient: bound to 192.168.100.11 -- renewal in 11 seconds.

If you see the pattern, then jump to the solution in the next section. If you do not see the pattern, your Internet connection problems are likely caused by another issue.

[edit] Solution

[edit] ClarkConnect 3.0 and Earlier

Add the following line to /etc/dhclient.conf (create the file if it does not exist):

reject 192.168.100.1;

[edit] ClarkConnect 3.1 & 3.2

Add the following line to /etc/dhclient-eth0.conf (create the file if it does not exist):

reject 192.168.100.1;

Change the filename if you use a different network interface for connecting to the Internet.