Cisco PIX 525 Spezifikationen PDF herunterladen (Seite 192)

5-16

Cisco PIX Firewall and VPN Configuration Guide

78-15033-01

Chapter 5 Configuring Application Inspection (Fixup)

Voice Over IP

H.323

This section describes how to manage application inspection for the H.323 suite of protocols. It includes

the following topics:

• Overview, page 5-16

• Multiple Calls on One Call Signalling Connection, page 5-16

• Viewing Connection Status, page 5-17

• Technical Background, page 5-17

Overview

You can use the fixup command to change the default port assignment for the H.323 protocol. The

command syntax is as follows:

[no] fixup protocol h323 h225 |ras port [-port]]

Use the port option to change the default control connection port assignment. The default port

assignments are as follows:

• h323 h225 1720

• h323 ras 1718-1719

Use the -port option to apply H.323 application inspection to a range of port numbers.

The fixup protocol h323 command provides support for H.323-compliant endpoints. PIX Firewall

Version 5.3 through Version 6.2 supports H.323 Version 2. PIX

Firewall Version 6.3 supports H.323

Version 3 and Version 4.

H.323 is a suite of protocols defined by the International Telecommunication Union (ITU) for

multimedia conferences over LANs. H.323 supports VoIP gateways and VoIP gatekeepers. H.323

Version 2 adds the following functionality:

• Fast Connect or Fast Start Procedure for faster call setup

• H.245 tunneling for resource conservation, call synchronization, and reduced set up time

Usage Notes

1. Static PAT may not properly translate IP addresses embedded in optional fields within H.323

messages. If you experience this kind of problem, do not use static PAT with H.323.

2. It has been observed that when a NetMeeting client registers with an H.323 gatekeeper and tries to

call an H.323 gateway that is also registered with the H.323 gatekeeper, the connection is established

but no voice is heard in either direction. This problem is unrelated to the PIX Firewall.

3. If you configure a network static where the network static is the same as a third-party netmask and

address, then any outbound H.323 connection fails.

Multiple Calls on One Call Signalling Connection

PIX Firewall Version 6.3 supports multiple calls on the same call signaling channel, a feature introduced

with H.323 Version 3. This feature reduces call setup time and reduces the use of ports on the

PIX

Firewall. A new timeout command is introduced to control how long the H.225 call signaling

channel stays open when using this feature. The syntax for this command is as follows:

timeout h225 hh[mm[ss]]

1 2 ... 187 188 189 190 191 192 193 194 195 196 197 ... 465 466

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