Installation guide

Preparing to Configure VoIP

Release 12.0(7)XK

Under most circumstances, the default voice-port command values are adequate to conﬁgure

FXO and FXS ports to transport voice data over your existing IP network. Because of the inherent

complexities involved with PBX networks, E&M ports might need speciﬁc voice-port values

conﬁgured, depending on the speciﬁcations of the devices in your telephony network.

7 Conﬁguring the H.323 Gateway

The gateway capability allows a Cisco MC3810 to function as an H.323 endpoint. Therefore, the

gateway provides admission control, and address lookup and translation.

Preparing to Conﬁgure VoIP

Before you can conﬁgure your Cisco MC3810 concentrator to use Voice over IP, you must ﬁrst:

• Establish a working IP network. For more information about conﬁguring IP, refer to the

“IP Overview,” “Conﬁguring IP Addressing,” and “Conﬁguring IP Services” chapters in the

Cisco IOS 12.0 Network Protocols Conﬁguration Guide, Part 1.

• Install a digital voice module (DVM) or an analog voice module (AVM) into the appropriate bays

of your Cisco MC3810 concentrator. For more information about the physical characteristics of

the voice modules, or how to install them, refer to the Cisco MC3810 Series Multiservice Access

Concentrators Hardware Installation Guide which came with your Cisco MC3810 concentrator.

• Complete your company’s dial plan.

• Establish a working telephony network based on your company’s dial plan.

• Integrate your dial plan and telephony network into your existing IP network topology. Merging

your IP and telephony networks depends on your particular IP and telephony network topology.

In general, Cisco recommends the following suggestions:

— Use canonical numbers wherever possible. It is important to avoid situations where

numbering systems are signiﬁcantly different on different routers or access servers in your

network.

— Make routing and/or dialing transparent to the user—for example, avoid secondary dial tones

from secondary switches, where possible.

— Contact your PBX vendor for instructions about how to reconﬁgure the appropriate PBX

interfaces.

After you have analyzed your dial plan and decided how to integrate it into your existing IP network,

you are ready to conﬁgure your network devices to support Voice over IP.

Conﬁguring IP Networks for Real-Time Voice Trafﬁc

You need to have a well-engineered network end-to-end when running delay-sensitive applications

such as VoIP. Fine-tuning your network to adequately support VoIP involves a series of protocols and

features geared toward quality of service (QoS). It is beyond the scope of this document to explain

the speciﬁc details relating to wide-scale QoS deployment. Cisco IOS software provides many tools

for enabling QoS on your backbone, such as Random Early Detection (RED), Weighted Random

Early Detection (WRED), Fancy queuing (meaning custom, priority, or weighted fair queuing), and

IP Precedence. To conﬁgure your IP network for real-time voice trafﬁc, you need to take into

consideration the entire scope of your network, then select the appropriate QoS tool or tools.

The important thing to remember is that QoS must be conﬁgured throughout your network—not just

on the Cisco MC3810 concentrator devices running VoIP—to improve voice network performance.

Not all QoS techniques are appropriate for all network routers. Edge routers and backbone routers