List at least four benefits of using H.323 as a gateway protocol.

• Caller ID from FXO and T1 CAS
• Use of a fractional PRI
• Interoperability with applications and devices from other vendors
• No version dependence between a gateway and CallManager
• Granular call control
• Tcl and VXML applications can be used
• Support for legacy systems
• Support for more types of TDM interfaces and signaling than MGCP
• Multimedia support
• NFAS support
• Use of a gatekeeper for call control and address resolution
• PRI call preservation

When you are configuring an H.323 gateway on a CallManager, what information do you enter for Device Name?

Enter the IP address of the gateway. If CallManager can reach the gateway with more than one IP address, use the h323-gateway voip bind srcaddr ip-address command to select which address to use.

Name four types of DTMF Relay that H.323 uses.

H.245 uses Cisco-RTP, RTP-NTE, H.245 Alphanumeric, and H.245 Signal.

What commands must you enter for a Cisco gateway to use H.323 Fast Start?

Cisco gateways assume that H.323 Fast Start is used. No commands are necessary to configure it.

Briefly describe toll bypass.

With toll bypass, calls between company locations are sent over the IP network as VoIP when bandwidth is available, and they are routed over the PSTN when no bandwidth is available.

If you configure conflicting commands globally under the voice service voip configuration mode, and under the dial peer using voice class, which commands will the router use?

The router will use the most explicating applied commands, which in this case are the commands under the dial peer. It will use global commands only if more explicit ones are not configured.

How do you prevent active calls from being terminated when the CallManager becomes unreachable?

Turn off H.225 keepalives between the gateway and CallManager. The commands to do this are as follows:

GW1(config)#voice service voip

GW1(conf-voi-serv)#h323

GW1(conf-serv-h323)#no h225 timeout keepalive