Cisco ASA Series Cli Configuration Manual page 1154

MGCP Inspection
Note
To avoid policy failure when upgrading from ASA version 7.1, all layer 7 and layer 3 policies must have
distinct names. For instance, a previously configured policy map with the same name as a previously
configured MGCP map must be changed before the upgrade.
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.
MGCP endpoints are physical or virtual sources and destinations for data. Media gateways contain
endpoints on which the call agent can create, modify and delete connections to establish and control
media sessions with other multimedia endpoints. Also, the call agent can instruct the endpoints to detect
certain events and generate signals. The endpoints automatically communicate changes in service state
to the call agent.
MGCP transactions are composed of a command and a mandatory response. There are eight types of
commands:
•
CreateConnection
•
ModifyConnection
•
DeleteConnection
•
NotificationRequest
•
Notify
•
AuditEndpoint
•
AuditConnection
•
RestartInProgress
The first four commands are sent by the call agent to the gateway. The Notify command is sent by the
gateway to the call agent. The gateway may also send a DeleteConnection. The registration of the MGCP
gateway with the call agent is achieved by the RestartInProgress command. The AuditEndpoint and the
AuditConnection commands are sent by the call agent to the gateway.
All commands are composed of a Command header, optionally followed by a session description. All
responses are composed of a Response header, optionally followed by a session description.
•
The port on which the gateway receives commands from the call agent. Gateways usually listen to
UDP port 2427.
•
The port on which the call agent receives commands from the gateway. Call agents usually listen to
UDP port 2727.
Note
MGCP inspection does not support the use of different IP addresses for MGCP signaling and RTP data.
A common and recommended practice is to send RTP data from a resilient IP address, such as a loopback
or virtual IP address; however, the ASA requires the RTP data to come from the same address as MGCP
signalling.
Cisco ASA Series CLI Configuration Guide
1-12
Chapter 1 Configuring Inspection for Voice and Video Protocols