Cisco Systems uBR7246 manual Set the Downstream Symbol Rate, Troubleshooting Tips

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Configure the Downstream Cable Interface

Troubleshooting Tips

If you are having trouble:

Make sure the cable connections are not loose or disconnected.

Make sure the cable modem card is firmly seated in its Cisco uBR7246 chassis slot.

Make sure that you have entered the correct slot and port numbers when you typed the command.

Make sure you have calculated and entered the center frequency for your headend accurately.

Set the Downstream Symbol Rate

You need to set the megasymbols per second (Msps) rate for a downstream port on a cable modem card. A symbol is the basic unit of modulation. QPSK encodes 2 bits per symbol, 16-QAM encodes 4 bits per symbol, 64-QAM encodes 6 bits per symbol, and 256-QAM encodes 8 bits per symbol. The valid range for the downstream symbol rate is 0 to 6,000,000 Msps.

Caution The default downstream symbol rate is set to comply with MCNS specifications for Annex B cable modem support at 5.056941 Msps with 64-QAM modulation and 5.36037 Msps with 256-QAM modulation. This command should only be used to change the symbol rate to support Annex A cable modems that are used outside North America.

To set the downstream symbol rate, use the following command in cable interface configuration mode:

Command

Purpose

cable downstream symbol-rate number

Set the downstream symbol rate for Annex A

 

(5.056944 Msps). Do not enter the decimal point in the

 

symbol rate.

 

 

Validation Tips

To verify the downstream symbol rate, enter the show controllers cable command for the downstream port that you have just configured:

router# show controllers cable 6/0 downstream

Cable6/0 Downstream is up

Frequency=96000000, Channel Width 6 MHz, 64-QAM, Symbol Rate 5.056941 Msps

FEC ITU-T J.83 Annex B, R/S Interleave I=32, J=4

Troubleshooting Tips

If you are having trouble:

Make sure the cable connections are not loose or disconnected.

Make sure the cable modem card is firmly seated in its Cisco uBR7246 chassis slot.

Make sure that you have entered the correct slot and port numbers when you typed the command.

Make sure you have selected the default if you are using Annex B cable modems.

Make sure that you have entered the correct symbol rate for Annex A specifications if you are using Annex A cable modems. Do not enter the decimal point when entering the symbol rate.

Make sure the downstream carrier is active by entering the cable downstream if-outputcommand.

VC-140Voice, Video, and Home Applications Configuration Guide

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Contents Page Topology for uBR7246 Universal Broadband Description of Cisco uBR7246 Cable Router Benefits of Cisco uBR7246List of Terms Prerequisite Tasks Configure the Downstream Cable Interface Supported MIBs and RFCsCommand Purpose Set the Downstream Center FrequencySet the Downstream Symbol Rate Troubleshooting TipsSet the Downstream Mpeg Framing Format Annex a or Annex B Set the Downstream ModulationSet the Downstream Interleave Depth Step Command Purpose Activate the Downstream CarrierConfigure the Upstream Cable Interface Set the Upstream FrequencySet the Upstream Input Power Level Activate Upstream Forward Error Correction Router# more systemrunning-config Activate the Upstream ScramblerActivate the Upstream Ports Configure and Activate Baseline Privacy Configure Kek Encryption Key Privacy Configure Traffic Encryption Key PrivacyConfigure and Activate Frequency Agility Activate Baseline PrivacyCreate Spectrum Groups Activate IP Address Resolution Protocol Configure and Activate Spectrum GroupsActivate Address Resolution Protocol Requests Activate Host-to-Host Communication Proxy ARPSet Optional IP Parameters Activate Proxy ARP RequestsActivate IP Multicast Echo Activate IP Broadcast EchoActivate Cable Modem Authentication Manage Cable Modems on the HFC NetworkActivate Cable Modem Upstream Address Verification Command Task Activate Cable Modem Insertion IntervalUniversal Broadband Features Configuration Example Enter the global configuration mode. configure terminal

uBR7246 specifications

The Cisco uBR7246 is a versatile edge router designed primarily for cable operators wishing to deliver high-speed Internet, telephony, and video services over hybrid fiber-coaxial (HFC) networks. This router is part of Cisco's extensive line of broadband access solutions, addressing the increasing demand for bandwidth among consumers and businesses alike.

One of the uBR7246's main features is its ability to support a wide range of broadband technologies including DOCSIS (Data Over Cable Service Interface Specification) and EuroDOCSIS. The router is designed to facilitate the delivery of high-speed data services while allowing for flexible configurations that adapt to evolving network technologies. This is crucial for operators looking to maximize their network efficiency and future-proof their infrastructure.

The uBR7246 is equipped with multiple modular slots, enabling service providers to customize the router according to their specific needs. High-capacity interface cards can be added to support various types of connections, such as Ethernet and TDM (Time Division Multiplexing), thus offering scalability. With support for both DOCSIS 1.0 and advanced versions like DOCSIS 3.0 and 3.1, the router can handle increased data rates and offer maximum efficiency in terms of bandwidth utilization.

Security features are integral to the uBR7246, as it employs advanced measures such as encryption and robust authentication protocols to ensure that subscriber data remains secure. This is particularly vital in an era where cyber threats are pervasive, and customer trust is essential.

In terms of performance, the uBR7246 offers exceptional throughput, capable of efficiently managing vast amounts of traffic without degradation of service. Advanced Quality of Service (QoS) mechanisms help prioritize traffic, ensuring that high-demand applications like video streaming and VoIP receive the necessary bandwidth they require for optimal performance.

The router is also designed with operational ease in mind, offering centralized management capabilities through Cisco's suite of management tools. This allows operators to monitor performance, manage configurations, and troubleshoot issues more efficiently, reducing downtime and enhancing service reliability.

In summary, the Cisco uBR7246 is a powerful and flexible solution that meets the demands of modern broadband delivery. Its advanced technologies, modular design, high-level security features, and robust performance make it an ideal choice for cable operators aiming to provide high-quality services to their subscribers while staying ahead of the competition.