Руководство По Проектированию для Cisco DNCS System Release 2.7 3.7 4.2
4000358 Rev B
Guidelines for Configuring the DBDS for DOCSIS
2-7
CMTS Configuration
Introduction
This section provides guidelines for configuring the CMTS to work with DHCTs in
Mixed DOCSIS/DAVIC mode or DOCSIS mode.
Interface Configuration
Either the first (.1) or last usable IP address (.254) from each network block is
typically configured as the gateway IP address for the end-user devices on each
cable interface card of a CMTS. In this example, the first usable IP address is
configured as the gateway IP address. When deploying the DOCSIS-capable DHCTs
the cable service operator should continue to configure their CMTS as they do today,
with the following modifications:
•
•
Implement any desired DSG definitions.
•
Add a new Gateway IP address (from the DHCT CPE subnet) for the DHCT CPE
at each CMTS RF interface.
•
Add a route pointing to the DNCS so that any packet from the DHCT CPE
destined to the DNCS is routed appropriately.
Global Configuration for the DOCSIS Set-top Gateway
As specified in DOCSIS Set-top Gateway (DSG) Interface Specification, the DSG is
intended to provide DOCSIS channel transport for out-of-band messaging that is
traditionally carried on dedicated channels. DSG definitions are established on the
CMTS to act as gateways for the DHCT broadcast, CA, OOB SI, and Passthru flows
that must be delivered to the DHCTs in each of the MAC domains of the CMTS.
The system operator chooses the DSG IP address from the DHCT CPE subnet on
The system operator chooses the DSG IP address from the DHCT CPE subnet on
each CMTS cable interface card that is needed to support DHCT CPEs. The examples
in this section use the second usable IP address (.2) from the DHCT CPE’s subnet.
The DNCS delivers the out-of-band data flows to each DSG IP address (taken from
The DNCS delivers the out-of-band data flows to each DSG IP address (taken from
the DHCT CPE subnet). The DSG definition defined on the CMTS then takes IP
packets destined for the DSG IP address and encapsulates them in an Ethernet
frame, using a well-known Cisco MAC address (00:01:A6:D0:0B:1E).
DHCTs operating in DOCSIS mode can receive DBDS broadcast data without
DHCTs operating in DOCSIS mode can receive DBDS broadcast data without
establishing an interactive communications path with the CMTS. In this scenario, the
DBDS supports DOCSIS DHCTs in a one-way operating environment (for example,
a reverse-path-impaired condition).