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Cisco Unified Border Element

Commonly Supported Fax/Modem Call Flow Configuration Examples

Document ID: 115742

Updated: Mar 31, 2014

Contributed by Hussain Ali, Cisco TAC Engineer.

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Introduction

This document lists the most commonly encountered fax/modem call flows for which Cisco customers open Technical Assistance Center (TAC) Service Requests (SRs), along with a baseline configuration that should be present on the gateways.

With the number of fax protocols supported by Cisco devices and service providers, it is easy to get confused with all the possibilities. The important point to note is that in a fax call flow, all the devices on VoIP need to utilize the same fax protocol for a fax call to be successful. Fax protocols, unlike audio calls, cannot be transcoded.

A fax call begins as an audio call and then switches over to a fax call. Two of the most common switchover mechanisms are Named Signalling Events (NSE) (Cisco propriety) and protocol-based (Standards) switchover. Just like the fax protocols, the switchover mechanism also needs to be the same in a fax call flow.

Acronym List

  • ATA186 - Analog Telephone Adaptor 186
  • ATA187 - Analog Telephone Adaptor 187
  • CUBE - Cisco Unified Border Element
  • CUCM - Cisco Unified Communications Manager
  • FXS - Foreign Exchange Station
  • GW - Gateway
  • ITSP - Internet Telephony Service Provider
  • MGCP - Media Gateway Control Protocol
  • PRI - Primary Rate Interface
  • SCCP - Skinny Client Control Protocol
  • SIP - Session Initiation Protocol
  • SIP/H323 - Session Initiation Protocol/Voice Class H323
  • VG224 - Voice Gateway 224
  • VG248 - Voice Gateway 248

Configure

In this section, you are presented with the information to configure the features described in this document.

Configurations

This document describes these configurations:

  • Telco - PRI - GW - FXS - Fax/Modem
  • Telco - PRI - GW - MGCP - CUCM - MGCP - VG224 - Fax/Modem
  • Telco - FXO - GW - H323/SIP - CUCM - SCCP - VG248 - Fax/Modem
  • Telco - PRI - GW - MGCP - CUCM - SCCP - ATA186 - Fax/Modem
  • Telco - PRI - GW - MGCP - CUCM - SIP - ATA187 - Fax/Modem
  • Telco - PRI - GW - SIP/H323 - CUCM - SIP - Fax Server
  • ITSP - SIP - CUBE - SIP/H323 - CUCM - SCCP - VG224
  • ATA186 - SCCP - CUCM - SIP - ATA187

Telco - PRI - GW - FXS - Fax/Modem

There are no Fax over IP (FoIP) protocols involved.

voice service potsfax rate disable

Telco - PRI - GW - MGCP - CUCM - MGCP - VG224 - Fax/Modem

This configuration performs both Passthrough (NSE) and T38.

The configuration for both GW and VG224 that do Modem Passthrough (NSE) is:

no ccm-manager fax protocol cisco
mgcp modem passthrough voip mode nse
mgcp modem passthrough voip codec g711ulaw

The configuration for both GW and VG224 that do T38 is:

no ccm-manager fax protocol cisco
no mgcp fax t38 inhibit
mgcp package-capability fxr-package
mgcp default-packagefxr-package
no mgcp fax t38 ecm

Telco - FXO - GW - H323/SIP - CUCM - SCCP - VG248 - Fax/Modem

This configuration performs both Passthrough (NSE) and T38 (NSE). Protocol-based switchover is not supported with SCCP.

The configuration for a GW that does Modem Passthrough (NSE) is:

dial-peer voice <tag> voip
modem passthrough nse codec g711ulaw

Or, if there is no specific configuration on the dial-peer, then this information displays when you enter the voice service voip command.

modem passthrough nse codec g711ulaw

The configuration for a VG248 that does Modem Passthrough (NSE) is:

  1. Configure > Telephony > Port specific parameters > Choose the port to which the fax machine is connected. Set Fax Relay to disabled.
  2. Configure > Telephony > Advanced Settings > Set Passthrough signaling to IOS Mode.

The configuration for a GW that does T38 (NSE) is:

dial-peer voice <tag> voip
fax protocol t38 nse ls-redundancy 0 hs-redundancy 0 fallback
pass-through <g711ulaw or g711alaw>
fax-relay ecm disable
fax-relay sg3-to-g3

Or, if there is no specific configuration on the dial-peer, then this information displays when you enter the voice service voip command.

fax protocol t38 nse ls-redundancy 0 hs-redundancy 0 fallback
pass-through <g711ulaw or g711alaw>
fax-relay ecm disable
fax-relay sg3-to-g3

The configuration for a VG248 that does T38 (NSE) is:

  1. Configure > Telephony > Port specific parameters > Choose the port to which the fax machine is connected.

    1. Set Fax Relay to T.38 peer to peer.
    2. Set Fax relay ECM to disabled.
    3. Set Fax relay NSF to override with 000000.
  2. Configure > Telephony > Advanced Settings > Set Passthrough signaling to IOS Mode.

Telco - PRI - GW - MGCP - CUCM - SCCP - ATA186 - Fax/Modem

This configuration performs Passthrough (NSE).

The configuration for a GW that does Modem Passthrough (NSE) is:

no ccm-manager fax protocol cisco
mgcp modem passthrough voip mode nse
mgcp modem passthrough voip codec g711ulaw

For an ATA186 that does Modem Passthrough (NSE), refer to Configuring and Troubleshooting the Cisco ATA 186 with Fax.

Telco - PRI - GW - MGCP - CUCM - SIP - ATA187 - Fax/Modem

This configuration performs both Passthrough and T38.

The configuration for a GW that does Modem Passthrough is:

no ccm-manager fax protocol cisco
mgcp modem passthrough voip mode nse
mgcp modem passthrough voip codec g711ulaw

The configuration for a GW that does T38 is:

no ccm-manager fax protocol cisco
no mgcp fax t38 inhibit
mgcp package-capability fxr-package
mgcp default-package fxr-package
no mgcp fax t38 ecmmgcp fax t38 nsf 000000

For ATA187, refer to Cisco ATA 187 Analog Telephone Adaptor Administration Guide for SIP, Version 1.0.

Telco - PRI - GW - SIP/H323 - CUCM - SIP - Fax Server

This configuration mostly uses T38, but you need to confirm this on the fax server.

The configuration for a GW that does T38 is:

dial-peer voice <tag> voip
fax protocol t38 ls-redundancy 0 hs-redundancy 0 fallback
pass-through <g711ulaw or g711alaw>
fax-relay ecm disable
fax-relay sg3-to-g3

Or, if there is no specific configuration on the dial-peer, then this information should display when you enter the voice service voip command.

voice service voip
fax protocol t38 ls-redundancy 0 hs-redundancy 0 fallback
pass-through <g711ulaw or g711alaw>
fax-relay ecm disable
fax-relay sg3-to-g3

ITSP - SIP - CUBE - SIP/H323 - CUCM - SCCP - VG224

VG224 needs to be an MGCP GW for this setup to work. NSE switchover is only specific to Cisco devices and providers do not support NSE based switchovers. Hence, this call flow will not work and VG224 must be converted to an MGCP GW for T38 faxing to work. After it is converted, the relevant faxing configuration will look as listed here.

The configuration for a CUBE that does T38 is:

dial-peer voice <tag> voip
fax protocol t38 ls-redundancy 0 hs-redundancy 0 fallback
pass-through <g711ulaw or g711alaw>
fax-relay ecm disable
fax-relay sg3-to-g3

Or, if there is no specific configuration on the dial-peer, then this information displays when you enter the voice service voip command.

fax protocol t38 ls-redundancy 0 hs-redundancy 0 fallback
pass-through <g711ulaw or g711alaw>
fax-relay sg3-to-g3

The configuration for a VG224 that does T38 is:

no ccm-manager fax protocol cisco
no mgcp fax t38 inhibit
mgcp package-capability fxr-package
mgcp default-package fxr-package
no mgcp fax t38 ecm

ATA186 - SCCP - CUCM - SIP - ATA187

The ATA187 needs to run firmware version 9.2.3 to support NSE based passthrough, otherwise integration is not possible.

Updated: Mar 31, 2014
Document ID: 115742