DHCP, DNS, TFTP, and TD Servers

Chapter 2 Preparing the Cisco uBR7225VXR Router for Installation

Provisioning the Cable Headend

A DHCP server must be installed at the headend. The DHCP server must also offer a time-of-day (TD) server option that is compliant with RFC 868.

In conjunction with the DHCP server, a Domain Name System (DNS) server must be installed to translate names of network nodes into IP addresses. A TFTP server must be installed to facilitate the transfer of DOCSIS configuration files over the broadband network.

Cisco provides a configuration tool with every Cisco uBR7225VXR universal broadband router—Cisco Network Registrar (CNR)—to automate dynamic IP address allocation to

cable interfaces, PCs, and other devices on the broadband network. CNR provides integrated DHCP and DNS services for your network configuration.

Telco Return

To support telco return, ensure that:

•Your downstream plant meets DOCSIS or EuroDOCSIS specifications.

•Your headend is wired for narrowcast downstream data transmission.

•You have assigned downstream frequencies.

•All equipment needed to support upstream traffic over the PSTN, as well as to monitor telco return service features is installed. Key components include:

–Dial-up access server (for example, the Cisco AS5300 or Cisco AS5800)

–RADIUS dial security server

•All third-party, telco return cable interfaces are DOCSIS-compliant.

•Your Cisco IOS software image supports telco return functionality.

The following sections describe CMTS equipment necessary to support telco return service.

Dial-Up/Remote Access Servers

Because a telco return cable network relies on the local telephone system to complete the upstream data path to the Cisco uBR7225VXR router, you need to be sure that you provision your network with a dial-up access server and other required equipment through which remote cable interfaces will gain access to your headend.

RADIUS Dial Security Servers

After remote telco return cable interfaces have initiated dial-up to the CMTS via the network access server, a RADIUS dial security server typically authenticates their respective usernames and passwords or MAC address and passwords and then determines whether or not to allow the connection.

In addition to the dial-up numbers provided in telephony channel descriptor (TCD) messages originating from the Cisco uBR7225VXR router, username and password information is included in TCD messages to validate the cable interface’s upstream connection. After dialing in to the network access server, the username and password portions of the TCD messages are passed through a RADIUS dial access server for authentication before the upstream data path can be completed. (See Figure 2-2.)

	Cisco uBR7225VXR Universal Broadband Router Hardware Installation Guide
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