Fax / Modem over IP

Introduction

This document provides a reference matrix for fax support in various Voice over IP (VoIP) gateways.

Prerequisites

Requirements

There are no specific requirements for this document.

Components Used

See the Fax Support Matrix section for more information on hardware and software versions.

The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.

Conventions

Refer to Cisco Technical Tips Conventions for more information on document conventions.

Fax Support Matrix

Integrated Services Router Fax Support Matrix:

Note: The Cisco 3825 can support one EVM-HD in either NME slot and the Cisco 3845 can support up to two EVM-HD in any two NME slots.

Matrix Table Notes

These notes apply to the matrix in this document:

• (*) Cisco 26xx, 36xx, 37xx, and AS5300 support gateway-controlled T.38 with MGCP from Cisco IOS Software Release 12.2(11)T. However, it is not supported in the Cisco CallManager network until Cisco IOS Software Release 12.2(11)T3 where "forced" T.38 mode has been added.

• (†) N/A with Cisco CallManager.

• When using Fax/Modem pass-through between Catalyst 6000/VG248 and Cisco IOS gateways, you need:

  • Voice Gateway Routers: Cisco IOS Software Release 12.2.11T or later is recommended

  • VG248: 1.2.1

• For Catalyst 6624, the loads A002030139S1 and A00203010041 are recommended.

• For Catalyst 6608, the loads D004030145S1 and D00403010047 are recommended.

• 3.2.(2c)SpD include loads D004030145S1 and A002030139S1.

• 3.1(4)SpA and 3.2(2c)SpF include D00403010047 and A00203010041.

• You must have Cisco CallManager version 3.1.3a or later to use fax pass-through mode on the Cisco ICS 7750.

T.38 Fax Relay Support with Cisco CallManager

The T.38 fax support with Cisco CallManager is as follows:

• With Cisco CallManager 4.2.3, the T.38 fax relay is supported as given here:

  • Cisco Unified CallManager supports CA-controlled MGCP T.38 fax relay.

  • Fax calls use T.38 in CA-controlled mode if IOS enables T.38 (default)

  • Fax calls use fax pass-through (or Cisco fax relay) if IOS disables T.38 (transparent to Cisco Unified CallManager)

  • Both H.323 and MGCP (IOS only) support T.38 fax relay. For T.38 fax relay interworking between H.323 gateways and MGCP gateways, ensure MGCP gateways are configured to operate in CA-controlled mode.

• With Cisco CallManager 5.0 and 5.1, the system supports both fax relay and fax pass-through. SIP Trunk supports calls that start as a voice call, then switch to T.38. In CallManager release 5.0, T.38 fax relay introduced this support:

  • SIP support through the SIP Trunk (configured by using SIP Trunk Configuration)

  • H.323 and SIP T.38 interoperability

  Note: Cisco Unified Communications Manager Release 5.0 does not include features from release 4.2(3). Release 6.0 includes those features.

• With Cisco CallManager 6.0, the same features are supported as in Cisco CallManager 4.2.3. In CallManager Release 6.0, T.38 fax relay added this support:

  • T.38 interoperability support between SIP and MGCP

Related Information

• Fax/Modem over IP Technical Support Pages
• Cisco IOS Fax Services over IP Roadmap
• Voice Technology Support
• Voice and Unified Communications Product Support
• Troubleshooting Cisco IP Telephony
• Technical Support & Documentation - Cisco Systems