Cisco Cisco IOS Software Release 12.1(1a)T1 Manuel Technique
How to Switch Over Cable Telco−Return to
Two−Way RF Return Path
Two−Way RF Return Path
Document ID: 12214
Contents
Introduction
Prerequisites
Requirements
Components Used
Conventions
Example of a Mixed Telco−Return and Two−Way Environment
Decision Process of the Cable Modem to Know If the System is Telco−Return or Two−Way Return
Path
Switching Modes in a Dual Telco−Return Modem Automatically
Ways of Switching the Dual Cable Modem from Telco−Return to Two−Way Modes Manually
Using the DOCSIS Configuration File
Using SNMP
Resetting to Factory Default
Related Information
Prerequisites
Requirements
Components Used
Conventions
Example of a Mixed Telco−Return and Two−Way Environment
Decision Process of the Cable Modem to Know If the System is Telco−Return or Two−Way Return
Path
Switching Modes in a Dual Telco−Return Modem Automatically
Ways of Switching the Dual Cable Modem from Telco−Return to Two−Way Modes Manually
Using the DOCSIS Configuration File
Using SNMP
Resetting to Factory Default
Related Information
Introduction
This document explains how to perform a cut−over from a Telco−Return (one−way) scenario to a two−way
Radio Frequency (RF) return path. In a two−way plant scenario, cable modems use an RF upstream instead of
an asynchronous Point−to−Point Protocol (PPP) return path via the Public Switched Telephone Network
(PSTN) (see Figure 1). This cut−over process is usually done after a cable plant has upgraded their
unidirectional amplifiers to bidirectional and can therefore support a RF transmission in both the forward and
return paths. The challenge for Multiple Service Operators (MSOs) is to make the cut−over with a minimal
impact to paying subscribers in a live Hybrid Fiber−Coaxial (HFC) network.
Radio Frequency (RF) return path. In a two−way plant scenario, cable modems use an RF upstream instead of
an asynchronous Point−to−Point Protocol (PPP) return path via the Public Switched Telephone Network
(PSTN) (see Figure 1). This cut−over process is usually done after a cable plant has upgraded their
unidirectional amplifiers to bidirectional and can therefore support a RF transmission in both the forward and
return paths. The challenge for Multiple Service Operators (MSOs) is to make the cut−over with a minimal
impact to paying subscribers in a live Hybrid Fiber−Coaxial (HFC) network.
Figure 1 − Telco−Return Diagram
The ability to perform such a cut−over seems complex physically, and may potentially interrupt service by
losing Internet connectivity for longer than desirable periods. However, this should not be the case if executed
correctly. This is because a Cisco uBR7246 Cable Modem Termination System (CMTS) can support both
modes: Telco−Return and two−way return paths mode at the same time on the same headend and the same
losing Internet connectivity for longer than desirable periods. However, this should not be the case if executed
correctly. This is because a Cisco uBR7246 Cable Modem Termination System (CMTS) can support both
modes: Telco−Return and two−way return paths mode at the same time on the same headend and the same