Cable Modems

This document addresses common connectivity-related questions and issues that new owners of uBR900 series cable modems may encounter. For information about other aspects of configuring and using uBR900 series cable modems, consult the following documents:

A. This depends on how your cable service provider has configured their network. In normal circumstances it should take less than five minutes for your uBR900 cable modem to come online from the time it is turned on; however, it is possible that it could take up to 15 minutes in rare circumstances.

A. The most common cause for this type of behavior is that the service provider does not have a record of your new cable modem's details, and so they view your uBR900 cable modem as unauthorized. Cable service providers can send a special parameter to unauthorized cable modems to stop them from passing data to the Internet.

When you try to connect a new cable modem to a cable system the first thing you need to do is make sure that your cable service provider has a record of your cable modem's details in their database. If your cable modem is not listed correctly in their system, then your cable modem is considered unauthorized and is not allowed to pass traffic to the Internet.

You can verify whether your cable service provider is allowing your uBR900 cable modem to pass traffic to the Internet by logging into the uBR900 cable modem and issuing the following enable mode command:

show controller cable 0 mac state | incl Access

In this first example, the uBR900 cable modem is allowed to pass data to the Internet because the Network Access attribute is set to TRUE.

Router> enable 
Router# show controller cable 0 Mac state | incl Access 
  Network Access:           TRUE 
Router#

In this second example, the uBR900 cable modem is not allowed to pass data to the Internet because the Network Access attribute is set to FALSE.

Router> enable 
Router# show controller cable 0 Mac state | incl Access 
  Network Access:           FALSE 
Router#

In this third example, the uBR900 cable modem has not yet come online properly because the show controller command returns no output. Consequently, the cable modem is unable to pass data to the Internet.

Router> enable 
Router# show controller cable 0 Mac state | incl Access 
Router#

The next most common cause for a PC not being able to get a DHCP lease or connect to the Internet is a poor connection between the cable modem's Ethernet port and the PC. While the PC is connected to the uBR900, the link LED on the front of the uBR900 cable modem, corresponding to the Ethernet port to which the PC is connected, should be lit up. If this is not the case, then replace the Ethernet cable between the PC and the uBR900 cable modem and verify that you are using a straight-through Ethernet patch cable. If this does not work, then connect the PC to a different Ethernet port on the uBR900 cable modem to see if this makes a difference.

Below is a picture of a uBR925 cable modem with a detailed view of the LED panel.

A. If your service provider is not willing to allow your uBR900 cable modem to connect to their system, then there is very little that you can do, and nothing Cisco can do. The service provider has complete control of what types of cable modems are allowed to connect to their system.