I need to create a dynamic dns rule in a thompson technicolor router. Problem is the ‘custom’ dns settings don’t let you actually change their default dns server. people have found they can telnet into the router and change the settings at the command line: see here

1. Telnet to the router IP address (normally 192.168.1.254):
telnet
o 192.168.1.254

2. Log into the router using appropriate login details (if unknown, try Username: Administrator, and no password)

3. List the current Dynamic DNS options
dyndns service list

4. Modify the custom option using this command:
dyndns service modify name=custom server=freedns.afraid.org port=www-http request=/nic/update updateinterval=7200

Replace values appropriately
server – the domain name of your Dynamic DNS provider
port – www-http
request – /nic/update [the path at your Dynamic DNS provider for DNS update calls]
updateinterval – number of seconds between updates from your router – default is 86000 (1 day)

5. Save changes to the router
saveall