Cisco 1841 and NTL Business Broadband Connection.

Hi,  I have a Cisco 1841 Router which I have been using to connect to BT broadband.  This has worked fine.  I have now changed Broadband suppliers to NTL, they use a Broadband Modem with a CAT 5 connection.  I have been trying to configure the Cisco router to use the NTL Broadband, when connected I can not see the internet.  I have come accross something strange with the NTL broadband, in the fact that I have been given 5 Static IP address, which can be registered with different equipment using the mac code.  I have a cheap netgear router, which when connected with the NTL broadband works fine, and looking in my service page on NTL is registering it MAC code with NTL and supplying it with an IP address, I can not edit this table manually and it seems to happen automactically but not with my Cisco.  If anyone can help me with this problem I would be most greatful.  Thanks AndyStart Free Trial