Cisco Digital 1-port and 2-port T1 Multi-Flex Voice WICs

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Introduction

The Cisco 1-port and 2-port T1 Multi-Flex Voice/WAN Interface Cards (Multi-Flex VWICs) support voice and data applications on a variety of Cisco multiservice platforms. These platforms include the Cisco 1700, 2600, 2600XM, 2691, 3600, and 3700 multiservice routers, as well as the Cisco VG200, WS-X4604-GWY, C4224, and ICS 7750 voice gateways. For more information on VWICs, refer to the Cisco One and Two Port T1/E1 Multi-Flex Voice/WAN Interface Card document.

A diagram shows a Cisco VWIC module with labels for AL, LP, CD, CTRLR T1 1, and CTRLR T1 0.

Prerequisites

There are no specific requirements for this document.

Components Used

This document is not restricted to specific software and hardware versions.

Conventions

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

Product Numbers

Features

The 1-port and 2-port T1 Multi-Flex Trunk VWICs differ from the T1 channel service unit/data service unit (CSU/DSU) (WIC-1DSU-T1). The T1 Multi-Flex Trunk VWICs can transmit either voice and data, or both, depending on the network module they are installed in and the presence of Digital Signal Processors (DSPs).

This Multi-Flex Trunk can function as a Voice Interface Card when combined with appropriate hardware such as an NM-HDV, NM-HDV2, NM-HD-2VE, or an AIM-VOICE-30 and AIM-ATM-VOICE-30 card. It can also be used as a WIC in a WIC slot on the Cisco 2600 or 3600 series routers, thus serving as a Voice WAN Interface Card (VWIC).

The Multi-Flex Trunk provides physical layer T1 access. The capabilities of the T1 interface are determined by the host system it is plugged into.

This Multi-Flex Trunk card does not support ISDN data or modem termination in a traditional Network Access Server (NAS) dial scenario. ISDN data and modem connectivity may be possible in specific scenarios when the VWIC is used for packet voice, such as with Modem Pass-through and Modem Relay to a peer voice gateway, but these features are outside the scope of this document.

Clocking Configurations

On the 2-port T1 Multi-Flex Trunk VWICs, there is a single shared clocking domain between the two T1 controllers. If both T1 controllers are configured to derive clocking from the line, the received clock references must be synchronous; otherwise, timing slips may occur on one or both controllers. If clocking sources are pleisochronous and one controller uses 'clock source line primary' while the other uses 'clock source line', the second controller might exhibit controlled slips in the output of the 'show controllers T1' command. This is a hardware limitation by design for the 2-port T1 Multi-Flex Trunk VWIC. Independent clocking sources are supported on the 2-port T1/E1 VWIC2 product when both controllers are used for data-only purposes.

Network Clock Participate

The network-clock-participate CLI command synchronizes the T1/E1 port's clocking with the TDM backplane switch. Routers like the 2600, 3600, 37xx, 28xx, and 38xx series feature a TDM backplane switch that supports voice traffic.

Clock Source Line Independent

For the VWIC2-2MFT card, the clock source line independent command addresses clocking issues encountered when the two ports of the VWIC are connected to different Telcos. This option allows independent clocking derivation for each port, placing them in separate clocking domains.

Effect of Clock Source Line Command

When the clock source line command is used with or without the independent option on both ports 0 and 1, the clock derived from port 0 will be loop-timed to port 1. For proper operation, both ports should derive clock from the same source to avoid clock slips. If ports 0 and 1 derive clock from different sources, the clock source line independent command should be applied to each port individually to enable independent clocking domains.

VWIC2-2MFT Independent Clock Source Option

When using two ports on the VWIC2-2MFT without the independent option, the clock from port 0 is loop-timed to port 1. To prevent clock slips, either:

• Use the independent option on the ports.
• Use the network-clock-participate command on the other end of the router (applicable for back-to-back connections).

Digital Voice Telephony

The Multi-Flex Trunk can serve as a Telephony interface for packet voice services when paired with compatible hardware that enables voice capabilities. This includes modules like the NM-HDV, NM-HDV2, NM-HD-2VE, AIM-VOICE-30, AIM-ATM-VOICE-30, and certain voice routers with integrated voice DSPs. When used as a Telephony interface for voice traffic termination, each DS0 can support one voice call. The T1 signaling capability (T1 CAS, ISDN PRI) is determined by the accompanying voice network module or multiservice gateway, not by the Multi-Flex Trunk itself.

When configured for ISDN PRI signaling, the card does not support ISDN data connections and cannot terminate ISDN 64 K or 56 K data connections. It exclusively supports voice-call termination with ISDN PRI signaling. Furthermore, the Multi-Flex Trunk, with or without voice-enabling hardware, cannot terminate modem connections on the router in a traditional NAS dial scenario.

Cisco 2600/2600XM/2691/3700 Chassis WIC Slot

When installed in a chassis WIC slot, each T1 on the Multi-Flex Trunk can be configured with a channel group to create a virtual serial interface. A 1-port VWIC T1 controller supports up to two channel groups, and a 2-port VWIC supports up to two channel groups on one T1 controller or one channel-group per T1 controller.

If the Cisco 2600/2600XM also has an AIM-VOICE-30 or AIM-ATM-VOICE-30 card, one T1 controller can be configured as an ISDN PRI or Channel Associated Signaling (CAS) Telephony voice interface. For the Cisco 2691/3700, which can accommodate multiple AIM VOICE cards, more than one T1 controller can be configured as an ISDN PRI or CAS Telephony voice interface. Specifics on interface-to-DSP resource mappings are beyond this document's scope.

Note: On the Cisco 2691/3700, two different ports and ds0-pri-groups can be mapped to the same AIM card's DSPs, which is not possible on the 2600s.

Note: To mix voice and data on the same VWIC mapped to an AIM, the AIM-ATM-VOICE-30 card must be used. The AIM-VOICE-30 card supports voice only.

NM-1E2W, NM-1E1R2W, and NM-2E2W

The Cisco 3600 NM-1E2W, NM-1E1R2W, and NM-2E2W support one serial channel group per WIC slot. The VWIC-2MFT-T1 is not supported, but the VWIC-2MFT-T1-DI is supported with one serial channel group.

NM-1FE2W, NM-1FE1R2W, NM-2FE2W, and NM-2W

The NM-1FE2W, NM-1FE1R2W, NM-2FE2W, and NM-2W Network Modules are supported on Cisco 2691/3600/3700 Multiservice Routers. The NM-2W Network Module is also supported on Cisco 2600/2600XM Multiservice Routers. When a VWIC is inserted into a WIC slot of these network modules, it can support two serial channel groups per WIC slot.

If the Cisco 2600/2600XM also has an AIM-VOICE-30 or AIM-ATM-VOICE-30 card, one T1 controller can be configured as an ISDN PRI or CAS Telephony voice interface. For the Cisco 3660/2691/3700, with multiple AIM VOICE cards, more than one T1 controller can be configured as an ISDN PRI or CAS Telephony voice interface. Specifics on interface-to-DSP resource mappings are beyond this document's scope.

Note: On the Cisco 2691/3700, two different ports and ds0-pri-groups can be mapped to the same AIM card's DSPs, which is not possible on the 2600s.

Note: To mix voice and data on the same VWIC mapped to an AIM, the AIM-ATM-VOICE-30 card must be used. The AIM-VOICE-30 card supports voice only.

Cisco 1721/1751/1760 Chassis WIC Slot

The Multi-Flex Trunk can be installed in chassis slot0 and slot1 WIC slots. Each T1 can be configured with a channel group to generate a virtual serial interface. A 1-port VWIC T1 controller supports up to two channel groups, and a 2-port VWIC supports up to two channel groups on one T1 controller or one channel-group per T1 controller.

If the Cisco 1751/1760 has voice DSPs installed, the Multi-Flex Trunk can be configured as a PRI or CAS voice Telephony interface. A 1-port T1 VWIC supports a single full PRI or a fractional PRI and a channel-group. A 2-port T1 VWIC supports up to two PRIs or one PRI and one channel-group.

Cisco WS-X4604-GWY, C4224, and ICS7750 WIC Slots

When inserted into the WIC slot of these Cisco devices, the VWIC Multi-Flex Trunk can be configured for either data or voice services. Consult the technical documentation for each product to determine specifics regarding the total number of channel-groups supported per T1 controller and permissible combinations of voice and data groups on 2-port VWICs.

• Configuring the Cisco ICS 7750 specifies that a data-only VWIC should be configured for a single channel-group. This is discussed in the "Configuring VWICs for Data-Only Transmission" section. "Configuring MRP and ASI Cards" discusses voice on the ICS 7750 (see "Configuring Digital Voice Ports").
• The capabilities of the VWIC Multi-Flex Trunk cards on the WS-X4604-GWY are detailed in "WS-X4604-GWY: Access Gateway Module (AGM) for Catalyst 4000 Series Switches" and the "Cisco Catalyst 4500 Series Access Gateway Module Data Sheet".
• The capabilities of the VWIC Multi-Flex Trunk cards on the Cisco C4224 are detailed in the "Catalyst 4224 Access Gateway Switch Software Configuration Guide", specifically the "Configuring the Data Interfaces" and "Configuring the Voice Interfaces" sections.

Two or More Channel Groups On One Port

Requirements

• Cisco IOS Software Release 12.1(1)T or later on the Cisco 2600
• Cisco IOS Software Releases 12.1(2)XH or 12.1(3)T or later on the Cisco 3620, 3640, and 3660 platforms
• Cisco IOS Software Release 12.2(8)T or later on the Cisco 2691 and 3700 platforms

Two channel groups on one port are supported in Cisco 2600, 2691, and 3700 chassis WIC slots.

• Not supported on NM-1E2W, NM-2E2W, or NM-1E1R2W.
• Supported on NM-1FE2W, NM-2FE2W, NM-1FE1R2W, and NM-2W.
• The WIC slot supports a maximum of two serial channel groups. In 2-channel group mode, only one physical port is supported by the WIC slot. Add/Drop multiplexing remains supported as only one port terminates on the router.
• The NM-HD-2VE and NM-HDV2 support up to 32 channel-groups. With the AIM-ATM-VOICE-30 card, a channel-group per timeslot (e.g., 60) is possible.

Drop and Insert

The Drop and Insert (D&I) feature allows DS0 timeslots to be extracted from one T1 interface and inserted into time slots of another T1 interface. This feature is available for VIC and WIC applications.

Drop and Insert functionality does not support different framing and line coding on the two ports. Therefore, when a tdm-group is configured on a T1 or E1 controller, the framing type between the two controllers must be identical. This applies only to the tdm-group functionality of the VWIC card.

Note: Configuring two different framing types will result in the following error message from the IOS:

Voice_Router (config)#connect TDM t1 0/1 t1 0/2
%CONN TDM: Framing type mismatch
%CONN TDM: Endpoints are incompatible
%CONN: Invalid Command

Drop and Insert timeslots do not need to be contiguous.

Drop and Insert of timeslots must occur on T1 controllers of the same 2-port VWIC, unless the gateway is Multiservice Interchange (MIX) enabled. If the gateway is MIX-enabled and TDM network clock participation is correctly configured, Drop and Insert of timeslots between T1 controllers on different VWICs is possible. Refer to "Multiservice Interchange (MIX) for Cisco 3600 Series Multiservice Platforms" for more details.

Drop and Insert utilizes tdm-groups.

Drop and Insert on a PRI is only possible if the entire PRI, including its D-channel, is D&I'd. If individual channels need to be D&I'd while other channels are terminated, PRI cannot be used; CAS must be used instead.

Additional Features

• BERT support requires Cisco IOS Software 12.1(1)T or later releases. Refer to V.54/BERT Multi-SCC for 1- and 2-Port T1/E1 Multiflex VWICs for more details.
• V.54 loopback requires Cisco IOS Software 12.1(1)T or later releases. Refer to V.54/BERT Multi-SCC for 1- and 2-Port T1/E1 Multiflex VWICs for more details.

Configuration

T1 Multi-Flex Trunk ports are configured differently from the T1 CSU/DSU WIC (WIC-1DSU-T1). T1 Multi-Flex Trunk ports are configured using controller t1 <slot>/<port>, similar to the Channelized T1/ISDN PRI Network Module. This configuration method does not imply that the VWIC supports ISDN PRI; protocol support is host-dependent.

Note: The commands for configuring Voice over IP (VoIP) on Cisco routers are generally consistent across router platforms, as detailed in the Platform Support section of this document.

Platform Support

This table outlines which routers support the 1 and 2 Port T1 Multi-Flex Trunk Voice/WAN Interface Cards, including Cisco IOS® Software Release support.

Footnotes:

• 1— Only 1 serial channel group is supported.
• 2—Not supported on Cisco 3660 with NM-1E1R2W, NM-1E2W, NM-2E2W in any Cisco IOS Software release.
• 4—Not supported in Cisco 1750. Cisco 1751 and 1760 support only voice applications in Cisco IOS Software Release 12.2(4)YB. Support for data and/or voice applications requires Cisco IOS Software Release 12.2(8)YJ. Refer to Cisco 1700 Series - Cisco IOS Release 12.2(4)YB.
• 5—Not supported in Cisco 1710 or 1720. Data only support for the Cisco 1721. Refer to Cisco IOS Software Release 12.2(8)YJ, Product Bulletin No. 1806.
• 6—2600XM platforms
• 7—The VWIC must be inserted into a chassis WIC slot or into an appropriate NM-xFEyR2W network module. On the Cisco 2600/2600XM only one T1 controller can be configured with a voice group; other platforms such as the Cisco 3660 (with MIX capability), 2691, and 3700 can have both T1 controllers on a 2-port VWIC configured for voice groups.
• 8—Cisco 3660 only with MIX capable chassis
• A note on MIX capable chassis: MIX-capable platforms include the Cisco 2691, 3725, and 3745. The Cisco 3660 can be made MIX-capable with the installation of a MIX-3660-64 unit.
• 9—Two AIM-VOICE-30 are needed to support this VWIC if both T1 controllers are to support full voice groups (all timeslots).
• 10—Cisco 2691
• 11—Cisco 3700 platforms
• 12—NM-HD-2VE only supported on Cisco 3660, 3640, 2600XM, 2691, and 37xx but not on Cisco 2600 and 3620/3640 platforms.
• 13—NM-HDV2 supported only on Cisco 2600xm, 37xx, and 2691

Digital Voice Port Pinout (RJ-48C)

The RJ-48C receptacles on the MFT are pinned out for customer premises equipment (CPE) rather than central office equipment. A T1/E1 crossover cable is required to connect to other CPE-pinned out equipment, such as PBXs.

Related Information

• Voice Hardware Compatibility Matrix for Cisco 1750, 2600, 3600 and VG200 Routers and Catalyst 4000, 5000 and 6000 Switches
• Voice Technology Support
• Voice and IP Communications Product Support
• Recommended Reading: Troubleshooting Cisco IP Telephony
• Technical Support & Documentation- Cisco Systems