Cisco 7200 Series Routers

PBX Interoperability Guidelines for the 7x00 Series Routers

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PBX Interoperability Guidelines for the 7x00 Series Routers

Table Of Contents

PBX Interoperability Guidelines
for the 7x00 Series Routers


T1 or E1 Selection

Chassis Clock Reference

Codec Complexity and DSPfarm

Data Support

PBX Interoperability Guidelines
for the 7x00 Series Routers

March 6, 2002


This document illustrates differences in configuring voice features on digital T1 interfaces or E1 interfaces on platforms using the High Density Voice Network Module (including Cisco 2600 and Cisco 3600 series routers), and those using Digital Voice Port Adapters (including Cisco 72xx, 7200VXR, and 75xx series routers). For interoperability with specific outside vendors, refer to the following URLs:

Alcatel 4400

Ericsson MD-100

Fujitsu 9600 ES

Lucent Definity G3R


Nortel Option 11C

Siemens Hicom 300 Series

Toshiba Strada DK424


All of the platforms mentioned share the same core set of high-level Cisco IOS voice and hardware features, since they use the same DSP (T1549) hardware and firmware. Thus, no differences exist in configuring the following features:

T1 or E1 controller configurations, such as line code, framing, clock, FDL,and cable length loopback

T1 or E1 signalling protocols, such as T1 CAS, FXS FXO, E&M, E1 R2, ISDN PRI and QSIG configurations using ds0-group or pri-group in controller mode

Voice-port related features like connection-trunk, comfort noise, echo cancellation, input gain, output attenuation, and signaling conditioning

TDM Drop and Insert

Dial-peer features such as codec selection, playout buffer, translation rules, fax, and DTMF relay

Common Voice over Packet features such as H.323, RTP, FRF.11 and FRF.12, GW/GK interaction

High-level applications like PBX trunking using Transparent-CCS, or hub and spoke VoFR applications

Some differences in configuring some features might occur. For example, support for newer software features, including, but not limited to, Advanced Voice Busyout, or Remote Telephony Survivability System, T.38 fax, or Interactive Voice Response, can be integrated into different Cisco IOS releases, since each platform has its own roadmap for the release of specific advanced features.

Some configuration commands, such as the ones used to configure low-level interface features, could also be different.

The following section will address these differences, using an example from a different platform, for replacing or upgrading a voice gateway.

T1 or E1 Selection

Because both PA-VX and PA-MCX are software configurable for T1 or E1 mode, a special command must be used to specify which standard is used. This is a global configuration mode command of the form:


card type [T1|E1] <slot no>


Controller type is not configurable

Chassis Clock Reference

Both the Cisco 7200VXR and the Cisco 3660 equipped with an MIX module, support an internal TDM bus which features multi-level clock source prioritization. An MIX-enabled T1 interface or E1 interface can be selected to provide clock resources for the entire chassis, or you can use the default of the internal PLL oscillator.

Cisco 7200VXR: Use a single global configuration command

frame-clock-select [T1 | E1] <slot> <priority>

Cisco 3660 with MIX module: Use the following two commands:

network-clock-participate nm <slot>
network-clock-select <priority> [T1 | E1] <slot/port>

Configuring an external clock source is not mandatory. However, when the circuits or devices connected to the Cisco 7200VXR drive their own clock and the router chassis uses the internal PLL, the T1 or E1 controller experience slips, indicating a clock discrepancy. A small number of slips will not affect voice quality, but they can severely impact the fax. Therefore, it is recommended that this command always be configured to have the T1 or E1 controller error-free.

Codec Complexity and DSPfarm

To configure the "codec algorithm complexity," which affects the number of voice channels that a single DSP can process, PA-VXC and NM-HDV use different configuration modes:


interface dspint dsifarm <slot/port>
	codec domplexity [medium | high]


voice-card <slot>
codec complexity [medium | high]

These commands will automatically appear in the configuration and do not require explicit configuration unless required by the application. The platforms which support DSP farming will also be configured with the modes described above. the PA-VX also supports reset and shutdown of individual DSP in this manner.

Data Support

The PA-VX does not support data connections (channel-group), but they are supported on both the PA-MCX and NM-HDV. To configure a PA-MCX for pure data service, use the options "data" as shown below. To configure a PA-MCX for mixed data/voice application, chose either the "cas-voice" or "ccs-voice", depending on the actual signaling protocol used on the line.


controller [T1|E1] <slot/port>
service-type [cas-voice | ccs-voice | data]


Does not need an explicit configuration for mixed voice/data applications