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transition deviceMGCP Gateway Fallback Transition to Default H.323 Session Application - Cisco
This document shows how to enable a Media Gateway Control Protocol
(MGCP) gateway to fallback to an H323 session application when the WAN
Transmission Control Protocol (TCP) connection to the primary Cisco CallManager
server is lost, and no backup Cisco CallManager server is available.
There are no specific prerequisites for this document.
The information in this document is based on the software and hardware
versions below.
Cisco IOS& Software Release
Cisco 3700 series router
Cisco CallManager 3.3 and later
Note:&Cisco IOS version 12.2(11)T is the minimum required Cisco IOS version
required to run MGCP fallback and Survivable Remote Site Telephony (SRST) on
the same box.
The information presented in this document was created from devices in
a specific lab environment. All of the devices used in this document started
with a cleared (default) configuration. If you are working in a live network,
ensure that you understand the potential impact of any command before using
for more information on document
conventions.
All active MGCP analog and T1 Channel-Associated Signaling (CAS) calls
are maintained during the fallback transition. Callers are unaware of the
fallback transition, and these active MGCP calls are cleared only when the
communicating callers hang up. Active MGCP PRI backhaul calls are released
during fallback .
Any transient MGCP calls (that is, calls that are not in the connected
state) are cleared at the onset of the fallback transition and must be
attempted again later.
This configuration provides basic connection services for IP telephony
traffic that passes through the gateway. When the local MGCP gateway
transitions into fallback mode, the default H.323 session application assumes
responsibility for handling new calls. Only basic two-party voice calls are
supported during the fallback period.
Except for ISDN T1 and E1 PRI calls, all the MGCP calls that are active
at the time of fallback are preserved, while transient calls are released. When
a user completes (hangs up) an active MGCP call, the MGCP application handles
the on-hook event and clears all call resources.
Note:&To find additional information on the commands used in this document,
( customers only)
This document uses the network setup shown in the diagram below.
This document uses the configurations shown below. The three
configurations enable the user to:
Enable fallback in the Cisco IOS gateway.
Configure MGCP-controlled POTS dial peers with "destination-patterns"
to handle outgoing calls via H.323 in case of fallback.
Configure Voice over IP (VoIP) dial peers to route incoming calls (to
IP phones) to a local router (Fallback Cisco CallManager server) which provides
backup for IP phones.
IOS Gateway
For Cisco IOS Software Release 12.3(13)T or earlier:
interface FastEthernet0/0
ip address 192.168.1.12 255.255.255.0
ccm-manager fallback-mgcp
call application alternate DEFAULT
!----H.323 is the default signalling protocol.
!--- An FXS-connected phone gets a dial-tone from the router
!--- instead of being instructed to do so via MGCP by
!--- Cisco CallManager.
For Cisco IOS Software Release 12.3(14)T or later:
R(config)#application
R(config-app)#global
R(config-app-global)#service alternate Default
POTS Dial Peers
dial-peer voice X pots
application mgcpapp
destination-pattern 0T
!----Note that the destination-pattern command is needed for
H.323 when the MGCP fallback happens.
port 2/0:15
forward-digits all
dial-peer voice X pots
application mgcpapp
destination-pattern 2000
!----Note that the destination-pattern command is needed for
H.323 when the MGCP fallback happens.
port 1/0/0
Note:&For Cisco IOS Software Release 12.3(7)T or later, the
application mgcpapp command must
not be applied to the POTS dial peer that supports PRI
The SRST configuration shown here is required for Cisco IP Phone
SRST Configuration
call-manager-fallback
!--- Enables SRST support and enters Cisco CallManager fallback mode.
max-conferences 8
ip source-address 192.168.1.12 port 2000
!--- 192.168.1.12 is the IP address of the Cisco IOS gateway through which it
!--- communicates with the Cisco IP Phones.
!--- Here, the Cisco IOS gateway is also configured as a Cisco CallManager fallback server.
max-ephones 10
The VoIP dial peer configuration shown here is required if you have
another local router connected to the Cisco IOS gateway and acting as a
fallback Cisco CallManager server. If this gateway itself acts as a fallback
Cisco Callmanager server by running SRST, then the following VoIP dial peer
need not be configured. Cisco IOS Software version 12.2(11)T is the minimum
required version to run MGCP fallback and SRST on the same box.
VoIP Dial Peers
dial-peer voice 5000 voip
destination-pattern 5...
!--- These are IP phone directory numbers.
session target ipv4: x.x.x.x
!--- x.x.x.x. represents the IP address
!--- of the fallback Cisco CallManager server.
If You Have Cisco CallManager V3.3, 4.x or
Create an SRST reference
From Cisco CallManager, click System and
On the Find and List SRST References page, click Add a
New SRST Reference.
On the SRST Reference Configuration page, enter a name in the
SRST Reference Name field and the IP address of the Cisco SRST
router in the IP Address field.
Click Insert.
Apply the SRST reference or the default gateway to one or more
device pools.
From Cisco CallManager, click System and
Device Pool.
On the Device Pool Configuration page, click on
the desired device pool icon.
On the Device Pool Configuration page, choose an
SRST reference or “Use Default Gateway” from
the SRST Reference field’s menu.
This section provides information you can use to confirm your
configuration is working properly.
Certain show commands are supported by the
( customers only)
, which allows you to view an
analysis of show command output.
These commands can be used to verify the MGCP fallback
configuration:
—Displays the detailed
configuration of all CiscoIP Phones, voice ports, and dial peers in your
network during Cisco CallManager fallback.
—Displays output for the
dial peers during CiscoCallManager fallback.
—Displays a list of Cisco
CallManager servers and their current status and
availability.
Note:&The show ccm-manager fallback-mgcp command
output shown here is taken before MGCP fallback happens.
mgcp-gateway# show ccm-manager fallback-mgcp
Current active Call Manager:
192.168.1.2
MGCP Fallback mode:
Enabled/OFF
Last MGCP Fallback start time:
Last MGCP Fallback end time:
When the connection to the Cisco CallManager is lost, and MGCP Fallback
kicks in, the output is as follows:
mgcp-gateway# show ccm-manager fallback-mgcp
Current active Call Manager:
MGCP Fallback mode:
Enabled/ON
Last MGCP Fallback start time:
05:58:48 UTC Oct 6 2004
Last MGCP Fallback end time:
05:56:30 UTC Oct 6 2004
This console message helps in verifying the MGCP fallback
operation.
Sep 23 16:35:34.707: %CALL_CONTROL-6-APP_NOT_FOUND: Application mgcpapp in dial-peer 1 not found.
Handing callid 98 to the alternate app default
Certain show commands are supported by the
( customers only)
, which allows you to view an
analysis of show command output.
Note:&Before issuing debug commands, refer to
—Displays debugging information about
the Cisco CallManager.
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Document ID: 30061