Configuring MGCP-Controlled Backhaul of BRI Signaling
The MGCP-Controlled Backhaul of Basic Rate Interface (BRI) Signaling in Conjunction with Cisco Unified Communications Manager feature provides MGCP service to remote-office gateways that connect by means of ISDN BRI trunks to a centralized Cisco Unified Communications Manager.
Feature benefits include the following:
Centralized call-management architecture, enabling a high degree of network control
Short voice cut-through times
Graceful evolution to new technology and to AVVID
Only the ETSI BRI basic-net3 switch type is supported.
Feature History for MGCP-Controlled Backhaul of BRI Signaling in Conjunction with Cisco Unified Communications Manager
This feature was introduced for Cisco Communications Manager 3.3(2) (formerly known as Cisco CallManager 3.3(2)).
This feature was integrated into Cisco IOS Release 12.3(2)T.
Support was added for Cisco Unified Communications Manager 4.1.
This feature was implemented on the Cisco 2600XM, Cisco 2691, Cisco 2800 series, Cisco 3700 series, and Cisco 3800 series.
Finding Support Information for Platforms and Cisco IOS Software Images
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For more information about this and related Cisco IOS voice features, see the following:
"Overview of Cisco Unified Communications Manager and Cisco IOS Interoperability" on page 13
Your software release may not support all the features documented in this module. For the latest caveats and feature information, see
Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to
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Prerequisites for MGCP-Controlled Backhaul of BRI Signaling
Cisco Unified Communications Manager
Cisco Unified Communications Manager 4.1(1) or a later release
Cisco Voice Gateway
20-MB flash memory
One of the supported combinations of BRI voice interface card (VIC) and network module:
VIC-2BRI-NT/TE or VIC-2BRI-S/T in NM-1V or NM-2V with Cisco IOS Release 12.3(11)T or a later release
VIC2-2BRI-NT/TE in NM-HD-1V, NM-HD-2V, NM-HD-2VE, or NM-HDV2 with Cisco IOS Release 12.4(2)T or a later release
EM-4BRI-NT/TE in EVM-HD-8FXS/DID with Cisco IOS Release 12.4(2)T or a later release
MGCP enabled globally in a VoIP network
MGCP control of dial peers and voice ports
MGCP single-point configuration enabled
For MGCP configuration instructions, see
"Configuring MGCP Gateway Support for Cisco Unified Communications Manager" on page 23
Restrictions for MGCP-Controlled Backhaul of BRI Signaling
BRI backhaul uses the enhanced interface numbering support available in Cisco IOS Release 12.3(11)T and later. Previous releases supported only the slot/subslot/port format with the subslot forced to 0 on the Cisco 2600 series, Cisco 3600 series, and Cisco 3700 series. Cisco IOS Release 12.3(11)T and later releases support both the slot/port and slot/subslot/port interface numbering formats for BRI backhaul.
Only the ETSI BRI Basic-NET3 switch type is supported.
BRI calls are cleared during MGCP gateway fallback and rehome because ISDN BRI L2 must be reinitiated and brought up again by the new L3 task.
Do not add the applicationmgcpapp command to voice dial peers that support BRI backhaul.
Information About MGCP-Controlled Backhaul of BRI Signaling
MGCP-Controlled Backhaul of BRI Signaling
The MGCP-Controlled Backhaul of BRI Signaling feature supports a centralized Cisco Unified Communications Manager architecture with BRI trunks connected to remote branch offices. Transporting signaling information from a branch-office MGCP gateway to a centralized media-gateway controller for processing is called backhaul. D-channel signal information is backhauled to Cisco Unified Communications Manager through a TCP session. All Q.931 messages are passed through the TCP connection between the Cisco MGCP gateway and Cisco Unified Communications Manager. The MGCP gateway neither parses nor has any knowledge of the contents of those messages.
This feature enables you to connect remote ISDN PBXs and key systems to a Cisco ISDN BRI network termination (network side) or PSTN Class 4/5 switch through a Cisco ISDN BRI terminal equipment (as user side) interface. External call-control entities, such as one or more Cisco Unified Communications Manager servers, provide voice service between local and remote branch offices.
The figure below depicts a typical network-side scenario. NT denotes network termination; TE denotes terminal equipment.
Figure 1. Typical ISDN BRI Network-Side Scenario
The figure below shows a typical user-side scenario.
Figure 2. ISDN BRI User-Side Scenario
The following is the sequence of events during normal backhaul:
A call comes in from the PSTN and passes over the BRI trunk to the MGCP gateway.
The MGCP gateway passes signaling information from the call across the WAN to the Cisco Unified Communications Manager at headquarters.
The Cisco Unified Communications Manager instructs the MGCP gateway on how to set up and manage the call.
The call is established.
How to Configure MGCP-Controlled Backhaul of BRI Signaling
Configuring the BRI Interface as an MGCP-BRI Backhaul Endpoint
Command or Action
Enables privileged EXEC mode.
Enter your password if prompted.
Router# configure terminal
Enters global configuration mode on the BRI slot and port.
Router(config)# interface bri 1/0
Configures the BRI interface as the MGCP-BRI backhaul endpoint.
syntax is platform-dependent; type ? to determine.
This command is supported only for a user-side ETSI NET3 switch-type.
(Optional) Clears the interface of any active calls. If there are no active calls, you can skip this step.
Router(config-if)# isdn switch-type basic-net3
Sets the central-office switch type on the ISDN interface to basic-net3.
Router(config-if)# isdn bind-L3 ccm-manager service mgcp
Sets ISDN L3 binding on the BRI interface.
Router(config-if)# no shutdown
Restarts the interface if it was previously disabled.
Router(config-if)# no mgcp
Disables all MGCP applications and protocols.
Restarts MGCP and reregisters the gateway to Cisco Unified Communications Manager.
Exits interface-configuration mode.
Verifying MGCP-BRI Backhaul Configuration
Use the showisdnstatus command to verify that Layer 2 is established and that Layer 3 is configured as Cisco Unified Communications Manager. This output displays only if TEI negotiation is performed at startup.
Router# show isdn status
ISDN BRI1/1 interface
dsl 1, interface ISDN Switchtype = basic-net3
L2 Protocol = Q.921 L3 Protocol(s) = CCM-MANAGER
Layer 1 Status:
Layer 2 Status:
TEI = 64, Ces = 1, SAPI = 0, State = MULTIPLE_FRAME_ESTABLISHED
Use this command only if TEI negotiation is done at startup. Otherwise, TEI negotiation is done when the first call is placed, so output shows Layer 2 with no TEI negotiated and Layer 3 as down.
Use the showccm-manager command to verify your Cisco Unified Communications Manager configuration on the gateway.
Router# show ccm-manager
MGCP Domain Name:3845-1.cisco.com
Priority Status Host
Primary Registered 10.3.102.99
First Backup None
Second Backup None
Current active Call Manager: 10.3.102.99
Backhaul/Redundant link port: 2428
Failover Interval: 30 seconds
Keepalive Interval: 15 seconds
Last keepalive sent: 20:58:35 UTC Sep 3 2004 (elapsed time:00:00:11)
Last MGCP traffic time: 20:58:35 UTC Sep 3 2004 (elapsed time:00:00:11)
Last failover time: None
Last switchback time: None
Switchback mode: Graceful
MGCP Fallback mode: Not Selected
Last MGCP Fallback start time: None
Last MGCP Fallback end time: None
MGCP Download Tones: Disabled
Configuration Error History:
Use the showccm-managerbackhaul command to display information about the BRI backhaul link.
Router# show ccm-manager backhaul
Backhaul Link info:
Link Protocol: TCP
Remote Port Number:2428
Remote IP Address: 10.3.102.99
Current Link State:OPEN
Packets recvd: 4
Recv failures: 0
Xmit failures: 0
BRI Ports being backhauled:
Slot 0, VIC 0, port 0
Slot 1, VIC 0, port 0
Use the showmgcpendpoint command to display a list of your MGCP endpoints.
Router# show mgcp endpoint
Tips for Troubleshooting MGCP-Controlled Backhaul of BRI Signaling
The table below lists commands that are available for troubleshooting your configuration.
Table 1 Troubleshooting Commands
Enables you to address poor voice quality. If your system uses a-law pulse-code modulation (PCM), use this command in interface-BRI configuration mode to reconfigure the BRI voice port in the gateway for a-law PCM. The system default is mu-law PCM.
Displays debugging information about Cisco Unified Communications Manager backhaul message packets.
Displays debugging information about ISDN L3 Q.931 message packets.
Displays debugging information about MGCP message packets.
Configuring SRTP Mode on Cisco IOS MGCP Gateways
SRTP mode provides secure VoIP calls by addressing security requirements for privacy, integrity, and confidentiality of voice conversations. IPsec, a standards-based set of security protocols and algorithms, ensures that signaling information that is sent between the gateway and Cisco Unified Communications Manager are encrypted. Media encryption using standards-based Secure Real-Time Transport Protocol (SRTP) ensures that media streams between supported devices are secure.
Perform this task to configure SRTP mode on the gateway.
Before You Begin
You should first establish an IPsec connection between Cisco Unified Communications Manager and the MGCP gateway before using the MGCP SRTP package. Otherwise, media keys are sent in clear text and your voice call is not considered secure.
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