SIP Configuration Guide, Cisco IOS Release 15M&T
Configuring SIP Support for Hookflash
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Configuring SIP Support for Hookflash

Contents

Configuring SIP Support for Hookflash

This chapter contains information about the SIP Support for Hookflash feature that allows you to configure IP Centrex supplementary services on SIP-enabled, Foreign Exchange Station (FXS) lines. Supplementary services for the SIP Support for Hookflash feature include the following:

  • Call hold
  • Call waiting
  • Call transfer
  • 3-Way conferencing

Use the service dsapp command to configure supplementary Centrex-like features on FXS phones to interwork with SIP-based soft switches. The SIP Support for Hookflash feature supports the concept of a dual-line (ACTIVE and STANDBY for active and held calls) for FXS calls to support supplementary services. Hookflash triggers supplementary services based on the current state of the call.

You can configure the service dsapp command on individual dial peers, or configure globally for all calls entering the gateway.

Prerequisites for SIP Support for Hookflash

All Hookflash Features for FXS Ports

  • Ensure that the gateway has voice functionality that is configurable for SIP.
  • Establish a working IP network. For information on configuring IP, see the Cisco IOS IP Configuration Guide, Release 12.3.
  • Configure VoIP.

Restrictions for SIP Support for Hookflash

  • Release by any party other than controller causes the conference to be released when Packet Voice Digital Signal Processor (DSP) Module (PVDM2) is used.
  • Release by any party on cascading 3-Way Conference, releases all the calls.
  • Invocation of features such as Call Hold, Blind Transfer, Semi-Attended Transfers after establishment of 3-Way Conference, releases all the calls.
  • Semi-attended transfer is not possible between users connected to gateways using G729 codec with CUCM. With G711 codec, semi-attended transfer is possible using CUCM.

Information About SIP Support for Hookflash

Use the service dsappcommand to configure supplementary Centrex-like services on FXS phones to interwork with SIP-based softswitches. Hookflash triggers supplementary features based on the current state of the call and provides a simulation of dual-line capability for analog phones to allow one line to be active while the other line is used to control supplementary IP Centrex services. Supplementary services for the SIP Support for Hookflash feature include the following:

Call Hold

With the Call Hold feature, you can place a call on hold. When you are active with a call and you press hookflash, and there is no call that is waiting, you hear a dial tone.

If there is a call on hold, the hookflash switches between two calls; the call on hold becomes active while the active call is put on hold.

If you have a call on hold and the call hangs up, the call on hold is disconnected.

Call Holding Flows

The sequence of placing a call on hold is summarized in the following steps:

  1. User A and user B are active with a call.
  2. By pressing hookflash, user A initiates a call hold.
  3. SIP sends a call hold indication to user B.
  4. User A can now initiate another active call (user C), transfer the active call (call transfer), or respond to a call-waiting indication.

Note


Use the offer call-hold command in sip-ua configuration mode to configure the method of hold used on the gateway. For detailed information on the offer call-holdcommand, see the Cisco IOS Voice Command Reference Guide.


  1. User A receives a second dial tone and presses hookflash.

The figure below shows the initiation of the calls hold sequence.



  1. User A and User B reconnect.

The figure below shows the calls on hold resume sequence.



The table below summarizes the hookflash support for Call Hold services.

Table 1 Call Hold Hookflash Services

State

Action

Result

Response to FXS Line

Active call

Hookflash

Call placed on hold for remote party.

Second dial tone for FXS phone.

Call on hold

Hookflash

Active call.

FXS line connects to call.

Call on hold and active call

Hookflash

Active and call on hold are swapped.

FXS line connects to previous held call.

On hook

Active call is dropped.

Held call still active. Reminder ring on FXS line.

Call on hold goes on hook

Call on hold is dropped.

None.

Active call goes on hook

Active call is dropped.

Silence. Reconnects to held call after the value you specify for disc-toggle-time expires. See "How to Configure Disconnect Toggle Time".

Call Waiting

With the Call Waiting feature, you can receive a second call while you are on the phone with another call. When you receive a second call, you hear a call-waiting tone (a tone with a 300 ms duration). Caller ID appears on phones that support caller ID. You can use hookflash to answer a waiting call and place the previously active call on hold. By using hookflash, you can toggle between the active and a call that is on hold. If the Call Waiting feature is disabled, and you hang up the current call, the second call will hear a busy tone.

The call-waiting sequence is summarizes in the following steps:

  1. User A is active with a call to user B
  2. User C calls user B
  3. User B presses hookflash.

The call between user A and user B is held.

  1. User B connects to user C.

The figure below shows the call waiting sequence.



The table below summarizes hookflash support for Call Waiting services.

Table 2 Call Waiting Hookflash Services

State

Action

Result

Response to FXS Line

Active call and waiting call

Hookflash

Swap active call and waiting call.

FXS line connects to waiting call.

Active call disconnects

Active call is disconnected.

Silence.

Waiting call goes disconnects

Stay connected to active call.

None.

Call disconnects

Active call is dropped.

Reminder ring on FXS line.

Call Transfers

Call transfers are when active calls are put on hold while a second call is established between two users. After you establish the second call and terminate the active call, the call on hold will hear a ringback. The Call Transfer feature supports all three types of call transfers--blind, semi-attended, and attended.

Blind Call Transfer

The following describes a typical Blind call-transfer scenario:

  1. User A calls user B.
  2. User B (transferrer) presses hookflash, places user A (transferee) on hold, and dials user C (transfer-to).

Note


User B will not hear alerting for the time you configure. See "How to Configure Blind Transfer Wait Time".


  1. Before the Blind call transfer trigger timer expires, user B disconnects, and the call between user A and user B is terminated.
  2. User A is transferred to user C and hears a ringback if user C is available. If user C is busy, user A hears a busy tone; if user C is not busy and answers, user A and user C connect.

The figure below shows the call sequence for a Blind call transfer.



Semi-Attended Transfers

The following is a typical semi-attended transfer scenario:

  1. User A calls user B.
  2. User B places user A on hold and dials user C.
  3. After user B hears a ringback and user C rings, user B initiates a transfer, and the call between user A and user B is terminated.
  4. User A is transferred to user C and hears a ringback if user C is available. If user C is busy, user A hears a busy tone.
  5. If user C is not busy and answers, user A and user C connect.

The figure below shows the call details for a semi-attended transfer.



Attended Transfers

The following describes a typical attended transfer:

  1. User A calls user B.
  2. User B places user A on hold and dials user C.
  3. After user C answers, user B goes on-hook to initiate a transfer, and the call between user A and user B is terminated.
  4. User A is transferred to user C. If user C is busy when user B calls, user A hears a busy tone.
  5. If user C is not busy and answers, user A and user C connect.

The figure below shows the call details for an attended transfer.



The table below summarizes the hookflash support for Call Transfer services.

Table 3 Call Transfer Hook Flash Services

State

Action

Result

Response to FXS Line

Active call

Hookflash.

Call placed on hold.

Second dial tone.

Call on hold and outgoing dialed or alerting, or active call

On hook.

Call on hold and active call transferred.

--

Call on hold and outgoing alerting call

Hookflash

Active call dropped.

FXS line connects to call o hold.

3-Way Conference

You can use the 3-Way Conference feature to establish two calls with a single connection so that all three parties can talk together. If the 3-Way Conference feature is disabled, a second hookflash will toggle between the two calls.


Note


The 3-Way Conference feature only supports those SIP calls using the g711 or g729 codecs. This feature also supports specification GR-577-CORE.


Setting Up a 3-Way Conference

The following describes a typical 3-way conference scenario:

  1. User A is talking with user B (a second-party call).
  2. User A presses hookflash, receives a dial-tone, and dials user C.
  3. User C answers. User A and user C are active in a second-party call.
  4. User A presses hookflash to activate a 3-way conference.

In other terminology, user A is the host or controller; user B is the original call, and user C is the add-on.


Note


The 3-Way Conference feature is available when the second-party call is outgoing. If the second-party call is incoming and you press hookflash, the phone toggles between the two calls.


The figure below shows the call details for 3-way conferencing.



The table below summarizes the hookflash support for 3-way conferencing services.

Table 4 3-Way Conference Hookflash Services

State

Action

Result

Response to FXS Line

Active call

Hookflash

Call place on hold.

Second dial tone

Call on hold and active call

Join call on hold and active call.

Media mixing of both calls

Terminating a 3-Way Conference

The table below summarizes the termination of a 3-way conference:

Table 5 3-Way Conference Termination

State

Action

Result

Response to FXS Line

Active 3-way conference

User A disconnects first

3-Way conference terminates; all users are disconnected.

Dial tone

User B disconnects first

User A and user C establish a second-party call.

FXS line connects user A and user C.

User C disconnects first

User A and user B establish a second-party call.

FXS line connects user A and user B.

User A presses hookflash

User C disconnects and user A and user B establish a second-party call.

FXS line connects user A and user B.

How to Configure and Associate SIP Support for Hookflash

This section describes the procedures for configuring and associating the SIP Support for Hookflash feature. These procedures include the following:

  1. Configuring supplementary service by using the service dsapp command.
  2. Associating the supplementary services with configured dial peers.

or

Associating the supplementary services as the global default application on a gateway.

This section provides configurations for the following supplementary services and provides configuration for associating supplementary services with dial peers:

How to Configure Call Hold

SUMMARY STEPS

    1.    enable

    2.    configure terminal

    3.    application

    4.    service dsapp

    5.    param callHold TRUE

    6.    exit


DETAILED STEPS
     Command or ActionPurpose
    Step 1 enable


    Example:
    Router> enable
     

    Enables privileged EXEC mode.

    • Enter your password if prompted.
     
    Step 2 configure terminal


    Example:
    Router# configure terminal
     

    Enters global configuration mode.

     
    Step 3 application


    Example:
    Router(config)# application
     

    Enters SIP gateway-application configuration mode.

     
    Step 4 service dsapp


    Example:
    Router(config-app)# service dsapp
     

    Enters DSAPP parameters mode.

     
    Step 5 param callHold TRUE


    Example:
    Router(config-app-param)# param callHold TRUE
     

    Enables call hold.

     
    Step 6 exit


    Example:
    Router (config-app-param)# exit
     

    Exits the current mode.

     

    How to Configure Call Waiting

    To enable call waiting for a DSAPP, follow these steps:

    SUMMARY STEPS

      1.    enable

      2.    configure terminal

      3.    application

      4.    service dsapp

      5.    param callWaiting TRUE

      6.    exit


    DETAILED STEPS
       Command or ActionPurpose
      Step 1 enable


      Example:
      Router> enable
       

      Enables privileged EXEC mode.

      • Enter your password if prompted.
       
      Step 2 configure terminal


      Example:
      Router# configure terminal
       

      Enters global configuration mode.

       
      Step 3 application


      Example:
      Router(config)# application
       

      Enters SIP gateway-application configuration mode.

       
      Step 4 service dsapp


      Example:
      Router(config-app)# service dsapp
       

      Enters DSAPP parameters mode.

       
      Step 5 param callWaiting TRUE


      Example:
      Router(config-app-param)# param callWaiting TRUE
       

      Enables call waiting.

       
      Step 6 exit


      Example:
      Router (config-app-param)# exit
       

      Exits the current mode.

       

      How to Configure Call Transfer

      SUMMARY STEPS

        1.    enable

        2.    configure terminal

        3.    application

        4.    service dsapp

        5.    param callTransfer TRUE

        6.    exit


      DETAILED STEPS
         Command or ActionPurpose
        Step 1 enable


        Example:
        Router> enable
         

        Enables privileged EXEC mode.

        • Enter your password if prompted.
         
        Step 2 configure terminal


        Example:
        Router# configure terminal
         

        Enters global configuration mode.

         
        Step 3 application


        Example:
        Router (config)# application
         

        Enters SIP gateway-application configuration mode.

         
        Step 4 service dsapp


        Example:
        Router(config-app)# service dsapp
         

        Enters DSAPP parameters mode.

         
        Step 5 param callTransfer TRUE


        Example:
        Router(config-app-param)# param callTransfer TRUE
         

        Enables call transfer.

         
        Step 6 exit


        Example:
        Router(config-app-param)# exit
         

        Exits the current mode.

         

        How to Configure 3-Way Conferencing

        SUMMARY STEPS

          1.    enable

          2.    configure terminal

          3.    application

          4.    service dsapp

          5.    param callConference TRUE

          6.    exit


        DETAILED STEPS
           Command or ActionPurpose
          Step 1 enable


          Example:
          Router> enable
           

          Enables privileged EXEC mode.

          • Enter your password if prompted.
           
          Step 2 configure terminal


          Example:
          Router# configure terminal
           

          Enters global configuration mode.

           
          Step 3 application


          Example:
          Router (config)# application
           

          Enters SIP gateway-application configuration mode.

           
          Step 4 service dsapp


          Example:
          Router(config-app)# service dsapp
           

          Enters DSAPP parameters mode.

           
          Step 5 param callConference TRUE


          Example:
          Router(config-app-param)# param callConference TRUE
           

          Enables 3-way conferencing.

           
          Step 6 exit


          Example:
          Router(config-app-param)# exit
           

          Exits the current mode.

           

          How to Configure Disconnect Toggle Time

          You can configure the time to wait before switching to a call on hold if an active call disconnects (commonly known as disconnect toggle time). You can configure a time-to-wait range between 10 (default) and 30 seconds.

          SUMMARY STEPS

            1.    enable

            2.    configure terminal

            3.    application

            4.    service dsapp

            5.    param disc-toggle-time seconds

            6.    exit


          DETAILED STEPS
             Command or ActionPurpose
            Step 1 enable


            Example:
            Router> enable
             

            Enables privileged EXEC mode.

            • Enter your password if prompted.
             
            Step 2 configure terminal


            Example:
            Router# configure terminal
             

            Enters global configuration mode.

             
            Step 3 application


            Example:
            Router (config)# application
             

            Enters SIP gateway-application configuration mode.

             
            Step 4 service dsapp


            Example:
            Router(config-app)# service dsapp
             

            Enters DSAPP parameters mode.

             
            Step 5 param disc-toggle-time seconds


            Example:
            Router(config-app-param)# param disc-toggle-time 20
             

            Sets the time to wait before switching to a call on hold, if the active call disconnects (disconnect toggle time). You can specify a disconnect toggle time between 10 (default) and 30 seconds.

             
            Step 6 exit


            Example:
            Router(config-app-param)# exit
             

            Exits the current mode.

             

            How to Configure Blind Transfer Wait Time

            To configure the time the system waits before establishing a call, so that you can transfer a call by placing the phone on hook, proceed with the following steps.


            Note


            The transferrer will not hear the alert for the time you configure because the system delays the call in case blind transfer is initiated.


            SUMMARY STEPS

              1.    enable

              2.    configure terminal

              3.    application

              4.    service dsapp

              5.    param blind-xfer-wait-time time

              6.    exit


            DETAILED STEPS
               Command or ActionPurpose
              Step 1 enable


              Example:
              Router> enable
               

              Enables privileged EXEC mode.

              • Enter your password if prompted.
               
              Step 2 configure terminal


              Example:
              Router# configure terminal
               

              Enters global configuration mode.

               
              Step 3 application


              Example:
              Router(config)# application
               

              Enters SIP gateway-application configuration mode.

               
              Step 4 service dsapp


              Example:
              Router(config-app)# service dsapp
               

              Enters DSAPP parameters mode.

               
              Step 5 param blind-xfer-wait-time time


              Example:
              Router(config-app-param)# param blind-xfer-wait-time 10
               

              Enables call waiting.

               
              Step 6 exit


              Example:
              Router (config-app-param)# exit
               

              Exits the current mode.

               

              How to Associate Services with a Fixed Dial Peer

              After you have enabled and customized your services on a gateway by using the service dsapp command, you must associate these services with configured dial peers. You can associate individual dial peers, or alternately, you can configure these services globally on the gateway (see "How to Associate Services Globally on a Gateway"). If you associate these services globally, all calls entering from the FXS line side and from the SIP trunk side invoke the service dsapp services.

              To configure a fixed dial peer used by DSAPP to set up a call to the SIP server (trunk) side, proceed with the following steps:

              SUMMARY STEPS

                1.    enable

                2.    configure terminal

                3.    application

                4.    service dsapp

                5.    param dialpeer dial-peer-tag

                6.    exit


              DETAILED STEPS
                 Command or ActionPurpose
                Step 1 enable


                Example:
                Router> enable
                 

                Enables privileged EXEC mode.

                • Enter your password if prompted.
                 
                Step 2 configure terminal


                Example:
                Router# configure terminal
                 

                Enters global configuration mode.

                 
                Step 3 application


                Example:
                Router(config)# application
                 

                Enters SIP gateway-application configuration mode.

                 
                Step 4 service dsapp


                Example:
                Router (config-app)# service dsapp
                 

                Enters DSAPP parameters mode.

                 
                Step 5 param dialpeer dial-peer-tag


                Example:
                Router(config-app-param)# param dialpeer 5000
                 

                Configures a fixed dial peer used by DSAPP to set up a call to the SIP server (trunk) side, where dial-peer-tag is the tag of the dial peer used to place an outgoing call on the IP trunk side. The dial-peer-tag must be the same tag as the dial peer configured to the SIP server.

                 
                Step 6 exit


                Example:
                Router(config-app-param)# exit
                 

                Exits the current mode.

                 

                How to Associate Services Globally on a Gateway

                After you have enabled and customized your services on a gateway by using the service dsapp command, you must associate these services with configured dial peers. You can associate individual dial peers ("How to Associate Services with a Fixed Dial Peer"), or alternately, you can configure these services globally on the gateway. If you associate these services globally, all calls entering from the FXS line side and from the SIP trunk side will invoke the service dsapp services.

                SUMMARY STEPS

                  1.    enable

                  2.    configure terminal

                  3.    application

                  4.    global

                  5.    service default dsapp

                  6.    exit


                DETAILED STEPS
                   Command or ActionPurpose
                  Step 1 enable


                  Example:
                  Router> enable
                   

                  Enables privileged EXEC mode.

                  • Enter your password if prompted.
                   
                  Step 2 configure terminal


                  Example:
                  Router# configure terminal
                   

                  Enters global configuration mode.

                   
                  Step 3 application


                  Example:
                  Router(config)# application
                   

                  Enters SIP gateway-application configuration mode.

                   
                  Step 4 global


                  Example:
                  Router (config-app)# global
                   

                  Enters SIP gateway-application-global configuration mode.

                   
                  Step 5 service default dsapp


                  Example:
                  Router (config-app-global)# service default dsapp
                   

                  Globally sets dsapp as the default application. All calls entering the gateway (from the FXS line side and the SIP trunk side) invoke the dsapp application.

                   
                  Step 6 exit


                  Example:
                  Router(config-app-global)# exit
                   

                  Exits the current mode.

                   

                  Verifying SIP Support for Hookflash

                  After the 3-way conference is established, perform this task to verify the codec used for the conference.

                  SUMMARY STEPS

                    1.    enable

                    2.    show call active voice compact


                  DETAILED STEPS
                    Step 1   enable


                    Example:
                    Device> enable
                              

                    Enables privileged EXEC mode.

                    Step 2   show call active voice compact


                    Example:
                    Device# show call active voice compact
                    
                    <callID>  A/O FAX T<sec> Codec       type        Peer Address       IP R<ip>:<udp>
                    Total call-legs: 3
                       6358  ANS   T209     g729br8      VOIP        P1006            9.40.3.244:16442
                       6359  ORG   T210     g729br8      TELE        P1995
                       6363  ORG   T175     g729br8      VOIP        P1111008       9.40.3.245:16386
                     

                    Troubleshooting SIP Support for Hookflash

                    You can use the following commands to troubleshoot the SIP Support for Hookflash feature:

                    • debug voice application session
                    • debug ccsip all(SIP message level debug)
                    • debug voice ccapi inout

                    Configuration Examples for SIP Support for Hookflash

                    Configuring Call Hold Example

                    Gateway#
                     configure terminal
                    Enter configuration commands, one per line. End with CNTL/Z.
                    Gateway(conf)#
                     application
                    Gateway(config-app)# service dsapp
                    Gateway
                    (config-app-param)# param callHold TRUE
                    

                    Configuring Call Waiting Example

                    Gateway#
                     configure terminal
                    Enter configuration commands, one per line. End with CNTL/Z.
                    Gateway(conf)#
                     application
                    Gateway(config-app)# service dsapp
                    Gateway
                    (config-app-param)# param callWaiting TRUE
                    

                    Configuring Call Transfer Example

                    Gateway#
                     configure terminal
                    Enter configuration commands, one per line. End with CNTL/Z.
                    Gateway(conf)#
                     application
                    Gateway(config-app)# service dsapp
                    Gateway
                    (config-app-param)# param callTransfer TRUE
                    

                    Configuring 3-Way Conferencing Example

                    Gateway#
                     configure terminal
                    Enter configuration commands, one per line. End with CNTL/Z.
                    Gateway(conf)#
                     application
                    Gateway(config-app)# service dsapp
                    Gateway
                    (config-app-param)# param callConference TRUE
                    

                    Configuring Disconnect Toggle Time Example

                    In this example, a disconnect toggle time is configured; the toggle time specifies the amount of time in seconds the system waits before committing the call transfer, after the originating call is placed on hook.

                    Gateway# configure terminal
                    Enter configuration commands, one per line. End with CNTL/Z.
                    Gateway(conf)# application
                    Gateway(config-app)# service dsapp
                    Gateway(config-app-param)# param disc-toggle-time 10
                    

                    Configuring Blind Transfer Wait Time Example

                    In this example, a blind transfer wait time is configured that specifies the amount of time in seconds the system waits before committing the call transfer after the originating call is placed on hook.

                    Gateway# configure terminal
                    Enter configuration commands, one per line. End with CNTL/Z.
                    Gateway(conf)# application
                    Gateway(config-app)# service dsapp
                    Gateway(config-app-param)# param blind-xfer-wait-time 10
                    

                    Configuring a Fixed Dial Peer Used for Outgoing Calls on SIP Trunk Side Example

                    In this example, a fixed dial peer is configured to set up the call to the SIP server (trunk) side.

                    Gateway# configure terminal
                    Enter configuration commands, one per line. End with CNTL/Z.
                    Gateway(conf)# application
                    Gateway(config-app)# service dsapp
                    Gateway(config-app-param)# param dialpeer 5000
                    

                    Associating Services with a Fixed Dial Peer Example

                    In this example, a fixed dial peer is configured to set up the call to the SIP server (trunk) side. The line in bold shows the dial peer statement.

                    Gateway# show running log
                    .
                    !
                    application
                     service dsapp
                     param dialpeer 1234
                     param disc-toggle-time 15
                     param callWaiting TRUE
                     param callConference TRUE
                     param blind-xfer-wait-time 10
                     param callTransfer TRUE
                    !
                    voice-port 1/0/0
                     station-id-name Example1
                     station-id number 1234567890
                    !
                    voice-port 1/0/1
                     station-id-name Example2
                     station-id number 1234567891
                    !
                    voice-port 1/0/2
                     station-id-name Example31
                     station-id number 1234567892
                    !
                    dial-peer voice 1234 voip
                     service dsapp
                     destination-pattern.T
                     session protocol sipv2
                     session target ipv4:10.1.1.1
                     dtmf-relay rtp-nte
                     codec g711ulaw
                    !
                    dial-peer voice 9753 voip
                     service dsapp
                     destination-pattern.T
                     session protocol sipv2
                     session target ipv4:15.0.0.15
                     dtmf-relay rtp-nte
                     codec g729r8
                    !
                    dial-peer voice 100 pots
                     service dsapp
                     destination-pattern.1234567890
                     port 1/0/0
                     prefix 1234567890
                    !
                    dial-peer voice 101 pots
                     service dsapp
                     destination-pattern.1234567891
                     port 1/0/1
                     prefix 1234567891
                    !
                    dial-peer voice 102 pots
                     service dsapp
                     destination-pattern.1234567892
                     port 1/0/2
                     prefix 1234567892
                    !
                    !
                    sip-ua
                     registar ipv4:10.1.1.1 expires 3600
                    !

                    Associating Services Globally on a Gateway Example

                    In this example, the gateway is associated globally with supplementary services. The lines in bold show the dial peer statement.

                    Gateway# show running log
                    .
                    !
                    application
                     service dsapp
                     param disc-toggle-time 15
                     param callWaiting TRUE
                     param callConference TRUE
                     param blind-xfer-wait-time 10
                     param callTransfer TRUE
                    !
                    voice-port 1/0/0
                     station-id-name Example1
                     station-id number 1234567890
                    !
                    voice-port 1/0/1
                     station-id-name Example2
                     station-id number 1234567891
                    !
                    voice-port 1/0/2
                     station-id-name Example31
                     station-id number 1234567892
                    !
                    dial-peer voice 1234 voip
                     service dsapp
                     destination-pattern 1800T
                     session protocol sipv2
                     session target ipv4:10.1.1.1
                     dtmf-relay rtp-nte
                     codec g729r8
                    !
                    dial-peer voice 9753 voip
                     service dsapp
                     destination-pattern.T
                     session protocol sipv2
                     session target ipv4:10.1.1.1
                     dtmf-relay rtp-nte
                     codec g711ulaw
                    !
                    dial-peer voice 100 pots
                     preference 8
                     service dsapp
                     destination-pattern.6234567890
                     port 1/0/0
                     prefix 6234567890
                    !
                    dial-peer voice 101 pots
                     preference 8
                     service dsapp
                     destination-pattern.6234567892
                     port 1/0/1
                     prefix 6234567892
                    !
                    dial-peer voice 102 pots
                     preference 8
                     service dsapp
                     destination-pattern.6234567893
                     port 1/0/2
                     prefix 6234567893
                    !
                    !
                    dial-peer hunt 2
                    !
                    sip-ua
                     registar ipv4:10.1.1.1 expires 3600
                    !

                    Additional References

                    The following sections provide references related to the SIP Support for Hookflash feature.

                    MIBs

                    MIB

                    MIBs Link

                    None

                    To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

                    http:/​/​www.cisco.com/​go/​mibs

                    Technical Assistance

                    Description

                    Link

                    The Cisco Technical Support website contains thousands of pages of searchable technical content, including links to products, technologies, solutions, technical tips, and tools. Registered Cisco.com users can log in from this page to access even more content.

                    http:/​/​www.cisco.com/​techsupport

                    Feature Information for SIP Support for Hookflash

                    The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

                    Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

                    Table 6 Feature Information for SIP Support for Hookflash

                    Feature Name

                    Releases

                    Feature Information

                    SIP Support for Hookflash

                    12.4(11)T

                    This feature was introduced. SIP Support for Hookflash feature allows you to configure IP Centrex supplementary services on SIP-enabled, Foreign Exchange Station (FXS) lines.

                    SIP Support for Hookflash

                    15.4(2)T

                    The feature was enhanced to support hookflash using G729 codec for 3-way conference.