Cisco PIX 525 Spezifikationen PDF herunterladen (Seite 195)

5-19

Cisco PIX Firewall and VPN Configuration Guide

78-15033-01

Chapter 5 Configuring Application Inspection (Fixup)

Voice Over IP

MGCP messages are transmitted over UDP. A response is sent back to the source address (IP address

and UDP port number) of the command, but the response may not arrive from the same address as the

command was sent to. This can happen when multiple call agents are being used in a failover

configuration and the call agent that received the command has passed control to a backup call agent,

which then sends the response.

Enabling MGCP Application Inspection

Enter the following command to enable application inspection for MGCP:

[no] fixup protocol mgcp [port[-port]]

Application inspection for MGCP is disabled by default. To use MGCP, you typically need to configure

at least two ports. One on which the gateway receives commands and one for the port on which the call

agent receives commands. Normally, a call agent will send commands to port 2427, while a gateway will

send commands to port 2727.

Neither NAT or PAT are supported by PIX Firewall Version 6.3 and lower.

To enable MGCP application inspection for call agents and gateways using the default ports, enter the

following commands:

fixup protocol mgcp 2427

fixup protocol mgcp 2727

Enter the following command to set the duration for the MGCP inactivity timer:

timeout mgcp hh[mm[ss]]

When the specified time elapses, the MGCP media ports are closed. The default is 5 minutes.

Note Enabling or changing the MGCP application inspection will have no effect until you reload the PIX

Firewall configuration.

Configuration for Multiple Call Agents and Gateways

Use the following commands to configure the PIX Firewall to support the use of multiple MGCP call

agents and gateways:

[no] mgcp call-agent ip_address group_id

[no] mgcp command-queue limit

[no] mgcp gateway ip_address group_id

Use the mgcp call-agent command to specify a group of call agents which can manage one or more

gateways. This information will be used to open connections for the call agents other than the one a

gateway sends a command to so that any of the call agents can send the response. The ip_address option

specifies the IP address of the call agent. The group_id option is a number from 0 to 4294967295. Call

agents with the same group_id belong to the same group.

Use the mgcp command-queue command to specify the maximum number of MGCP commands that

will be queued waiting for a response The range of allowed values for the limit option is 1 to

4294967295. The default is 200. When the limit has been reached and a new command arrives, the

command that has been in the queue for the longest time will be removed.

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