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STCAPP how to configure fxs ports on CUCM



STCAPP feature allows CUCM to control analog phones through FXS ports in a Voice Gateway. This is done using SCCP protocol, so at the end, the analog port (FXS) will register to the CUCM server.


  • Cisco IOS 12.3(11)T or later in Voice Gateway
  • Cisco Unified Communications Manager 4.2 or later
  • At least 1 FXS port & available DSP’s for voice conversion

Voice Gateway Configuration

 First we need to configure SCCP on the Voice GW:

Select the interface that points to the CUCM where the analog phone will be registering to:

Router(config)# sccp local FastEthernet0/0

Point the VG to the IP address of the CUCM. Configure different CUCM servers with different identifier numbers and select the appropriate CUCM version:

Router(config)# sccp ccm identifier 10 version 7.0+

Enable SCCP protocol on the router:

Router(config)# sccp

Create a CCM group with its identifier number (Range 1 to 50):

Router(config)# sccp ccm group 1

Within the CCM group, associate the CUCM server ID in order of priority:

Router(config-sccp-ccm)# associate ccm 10 priority 1

Here is an example of the configuration with 3 CUCM servers:

sccp local loopback0

sccp ccm identifier 10 version 7.0+

sccp ccm identifier 11 version 7.0+

sccp ccm identifier 12 version 7.0+



sccp ccm group 1

associate ccm 10 priority 1

associate ccm 11 priority 2

associate ccm 12 priority 3


Now we’re going to enable the STC Application for Analog FXS ports.

Associate the STC Application with the CCM-group that controls calls & features:

Router(config)# stcapp ccm-group 1

Enable the STC Application:

Router(config)# stcapp

Configure a dial-peer for the voice port and activate STCAPP:

Router(config)#dial-peer voice 1 pots

Router(config-dial-peer)#service stcapp

Router(config-dial-peer)#port 0/1/0

Enable caller ID for that voice port

Router(config)#voice-port 0/1/0

Router(config-voice-port)# caller-id enable

Here is an example of the configuration for voice port 0/3/0:

stcapp ccm-group 1



voice-port 0/3/0

caller-id enable


dial-peer voice 1 pots

service stcapp

port 0/3/0


CUCM Configuration


1. Add a new gateway in CUCM administration page:


Select Voice Gateway type you are using from the drop down menu

  • Select SCCP from the protocol drop down menu
  • In the next screen, fill the requested MAC address. In this field use the last 10 Digits of your MAC address (To find the MAC address of the VG, use the ‘show interface’ command – make sure to use the interface selected as source in the VG configuration)
  • Select the call manager group from the drop down menu (that matches the CUCM servers and order configured in the VG configuration)
  • Select the correct modules and find the appropriate sub-units in the drop down menu. This configuration will change for each VG being used (you can run the ‘show diag’ output from the gateway to figure this out). For example, select 24 FXS SCCP if you are using a VG224 gateway.

* Note how the actual gateway name will display SKIGW along with the 10-digit MAC address

2. Finally, add and register the FXS voice ports

  • From the gateway just added, select the port that you want to configure
  • Select the Device Pool, calling search space, Device Security profile and all other settings as required
  • Add new DN on Line 1 – Enter your Directory number
  • Change maximum number of calls to 2 at the bottom of the page if needed (this is also required for call transfer, conference, etc)
  • Repeat these steps for each port you want to configure.
  • At the end go back to your Gateway page and apply config – now you can go to the port and you should confirm that the port is registered with your primary call manager IP address

* Note how the actual FXS endpoint names automatically takes the GW MAC address

Important things to keep in mind:

  • The CUCM gateway configuration will vary depending on the Router being used
  • No additional dial peers are needed to establish the connection
  • The Voice gateway might also have other analog/digital ports being used for other voice protocols. This means the VG can be also configured for H323, MGCP or SIP.


I am trying to add the SCCP gateway the SCCP is configured on the loopback in 4331. What will be the MAC of that gateway in CUCM?
I can find it using "sh stcapp device summary" but is there any other way to find the MAC if the SCCP is bind to the loopback interface?

I am trying to set this up so I can have an analog extension log in and out of a hunt group.  My gateway is a VG310 setup as MGCP.  Does it have to be assigned in CUCM as SCCP protocol?

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