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Chapter 1

Using the Cisco Voice Gateway 200

Using a Cisco VG200 Gateway with H.323

1-8

Software Configuration Guide for the Cisco VG200

78-10322-02

When you use a Cisco VG200 gateway with Cisco CallManager, you can use its
redundant call agent feature to eliminate a potential single point of failure in the
VoIP network. This feature requires that you have two or three Cisco CallManager
servers available on your network and that you identify each of these servers using
CLI commands. You identify the primary Cisco CallManager server as the MGCP
call agent, and identify the second and third Cisco CallManager servers as backup
servers.

Once the redundant call agent feature is configured, if the primary
Cisco CallManager server becomes unavailable, the Cisco VG200 gateway will
register with the backup Cisco CallManager server. The Cisco VG200 gateway
monitors MGCP packets sent by the Cisco CallManager and when no such traffic
is detected, it sends keepalive packets to which the Cisco CallManager server
should respond. If the Cisco VG200 gateway does not detect any packets from the
Cisco CallManager for a specified period, it will try to establish a new connection
with the backup Cisco CallManager server.

Another feature of the Cisco VG200 is called switchback, which refers to the way
that the gateway reestablishes a connection with the primary Cisco CallManager
server when the primary server becomes available again. You can configure the
Cisco VG200 to reestablish connection immediately, or to wait for a specified
length of time to ensure greater stability in the voice network.

Using a Cisco VG200 Gateway with H.323

The Cisco VG200 functions as an H.323 gateway with the following voice
interface types, which are currently not supported with MCGP:

E1 (R2 and E&M analog emulation)

T1-CAS (FXO, FXS, and E&M emulation)

E1-PRI

T1-PRI

ISDN/BRI

E&M

Note that H.323 configuration is more complicated compared to MGCP and does
not provide for redundant call agents. The following sections describe how to use
the Cisco VG200 with H.323 with various interface and signalling types:

Summary of Contents for VG200

Page 1: ...Overview page 1 1 Using the Cisco VG200 with Cisco CallManager page 1 6 Using the Cisco VG200 with MGCP page 1 7 Using a Cisco VG200 Gateway with H 323 page 1 8 Where to Go Next page 1 14 Voice over IP Overview Voice over IP VoIP enables your gateway to carry live voice traffic for example telephone calls and faxes over an IP network VoIP can consolidate voice and data traffic for more efficient u...

Page 2: ... network is properly tuned to reduce congestion Voice traffic is more sensitive to congestion than data traffic meaning that users will notice more congestion when using VoIP telephones than when using IP for other purposes For more information about configuring IP refer to the Configuring IP chapter in the Cisco IOS 12 0 Network Protocols Configuration Guide You also need to thoroughly understand...

Page 3: ...and PC based soft phones to exchange calls with users of plain old telephone service POTS phones on the PSTN The gateway translates between the signals used on the PSTN and the IP packets used to transmit data on a TCP IP network The H 323 Standard The H 323 standard describes a method for converting between voice and data transmission formats and for managing connections between telephony endpoin...

Page 4: ...ndwidth and provides a central point for call administration H 323 proxy An H 323 endpoint that acts as an intermediary between H 323 endpoints and other IP telephony devices To standardize communication among these devices and endpoints H 323 utilizes the following protocols H 245 Used to negotiate channel usage and capabilities H 225 Used for call signaling and call setup Registration Admission ...

Page 5: ...ion and improves reliability and performance In particular it makes configuration and administration of gateway devices easy With MGCP gateways are defined by MGCP as slave devices in relation to the master referred to as a call agent which manages connections between endpoints and controls how gateways function Figure 1 3 MGCP Because an MGCP gateway is a slave device it derives most of the confi...

Page 6: ...ones Cisco IP Phones or any H 323 compliant telephony devices The Cisco VG200 provides a 10 100BaseT Ethernet port for connection to the data network and a number of different telephony interfaces depending on the hardware and software configuration you choose Figure 1 4 Using the Cisco VG200 with Cisco CallManager Currently the Cisco VG200 supports the following types of analog ports and connecti...

Page 7: ... gateway with information about Cisco CallManager using the Cisco IOS command line interface CLI The procedures and commands required to perform this configuration are described in Chapter 3 Configuring Voice over IP When used with MGCP you must also configure the Cisco CallManager server with information about each port on a Cisco VG200 gateway using the Cisco CallManager Administrator a Web base...

Page 8: ...ted it sends keepalive packets to which the Cisco CallManager server should respond If the Cisco VG200 gateway does not detect any packets from the Cisco CallManager for a specified period it will try to establish a new connection with the backup Cisco CallManager server Another feature of the Cisco VG200 is called switchback which refers to the way that the gateway reestablishes a connection with...

Page 9: ...S 0 groups can be used to emulate an FXO analog connection to the PSTN an FXS analog connection to a T1 channel bank or an E M connection for enabling a trunk tie line When you configure your DS 0 groups you can configure DS 0 hunt groups which allow any available voice port to be used for a range of phone numbers This eliminates the chance that a single DS 0 could fail or that a DS 0 is busy at t...

Page 10: ...dpoint and coder decoder CODEC for each incoming call on each DS 0 group This is a straightforward task but this method of configuration does not take full advantage of the Cisco CallManager and can only be used for H 323 endpoints You can configure a Cisco VG200 gateway to direct all incoming calls to the Cisco CallManager and configure your dial plan using the Cisco CallManager Administrator Thi...

Page 11: ...can be routed and set up between endpoints on the VoIP network and the POTS devices on the T1 channel bank Figure 1 6 Using FXS Analog Emulation with T1 CAS E M Emulation As shown in Figure 1 7 you can use the T1 CAS port on a Cisco VG200 gateway with E M analog emulation E M signalling emulation lets you use a Cisco VG200 gateway to interconnect H 323 devices on a VoIP network with POTS devices o...

Page 12: ...ted to the voice network by an E M interface Both the Salt Lake City and the San Jose offices are using E M Port Type II with four wire operation and Immediate Start signaling Each E M interface connects to the gateway using two voice interface connections Users in San Jose dial 8 569 and then the extension number to reach a destination in Salt Lake City Users in Salt Lake City dial 4 527 and then...

Page 13: ...sure that the telephony port still accepts DTMF signals Direct Inward Dialing on a BRI Port The following example shows how to configure a BRI port for direct inward dialing DID This configuration allows the called number information from the ISDN Q 931 setup message to be used for routing on an ISDN line In this example a call comes in to gateway 1 on the BRI port The DID information allows the g...

Page 14: ...es the procedures required to configure your Cisco VG200 gateway however you choose to use it Even if you are familiar with other Cisco products you should refer to Chapter 2 because the configuration of a Cisco VG200 gateway is a little different from Cisco routers After completing the basic configuration required to use a Cisco VG200 gateway you can refer to Chapter 3 Configuring Voice over IP f...

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