Specifications

List of Terms
Bridging and Routing Features for the Cisco uBR904 Cable Modem 5
• Cable Device MIB—Records statistics related to the configuration and status of the
Cisco uBR904 cable modem. Statistics include an events log and device status. The Cable Device
MIB is very similar to the RFI MIB in that both allow access to statistics; they are different in
that the Cable Device MIB reports statistics on the cable modem, while the RFI MIB reports
statistics on the radio frequency transmissions over the cable television line.
Functional Description
The Cisco uBR904 cable modem is the end-user part of the Cisco data-over-cable system; it is also
referred to as a subscriber unit. The subscriber unit functions as an interface between the subscriber’s
personal computer(s) at the small office/home office and the cable operator’s network (the headend).
The Cisco uBR904 has a single-cable F-connector interface for connection to the HFC network and
a built-in Ethernet 10BaseT hub that provides four RJ-45 ports to which subscriber devices can be
connected. All four ports are treated as one Ethernet interface by the Cisco IOS software. More hosts
can be connected to the unit by connecting one of the 10BaseT ports to a hub. An additional RJ-45
port provides a console interface for configuration and diagnostic purposes.
In compliance with MCNS requirements, the cable interface requires no configuration or setup
procedures other than connecting the Cisco uBR904 to the cable system. The unit is configured
automatically using a configuration file generated by the cable service provider and delivered via the
Cisco uBR7246 universal broadband router installed at the cable headend. The headend router
provides a path from the cable modem to the DHCP server for PC address assignment.
The personal computer(s) connected to the cable modem must be configured for Internet Protocol
(IP). In addition, the cable service provider must have a correctly configured network Dynamic Host
Configuration Protocol (DHCP) server and EIA downstream channel. Using DHCP, the universal
broadband router assigns an IP address to the cable modem each time it connects to the network. The
IP address identifies the computer on the network and enables the universal broadband router to
route data to and from the PC.
After the cable modem is installed and the connected PC is configured for IP, and after DHCP
services are enabled and communication to the headend is established, the Cisco uBR7246 universal
broadband router downloads configuration information to the cable modem. The initial
configuration connection to the headend can take several minutes.
See Figure 3 for a sample network topology.