Interface and Hardware Component Configuration Guide, Cisco IOS Release 15M&T
Circuit Emulation over IP
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Circuit Emulation over IP

Contents

Circuit Emulation over IP

Circuit Emulation over IP (CEoIP) provides a virtual circuit through an IP network--similar to a leased line--to integrate solutions that require a time-sensitive, bit-transparent transport into IP networks. Data, with proprietary framing or without, arrives at its destination unchanged; the transport is transparent to the destination.

Finding Feature Information

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 www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

Prerequisites for Circuit Emulation over IP

  • The CEoIP feature requires a CEoIP network module (NM) on each end of the connection, either the NM-CEM-4TE1 NM or the NM-CEM-4SER NM. You do not need to use the same type of CEoIP NM on both ends of the connection.

  • The CEoIP feature requires 300 KB of flash memory and 1 MB of DRAM in addition to your Cisco IOS software requirements.

Restrictions for Circuit Emulation over IP

  • NM-CEM-4TE1 supports only B8ZS (T1) and HDB3 (E1) line codes.

  • E1 lines do not support 56 kbps connections.

  • CEoIP software cannot run payload compression for more than 3.088 Mbps) per network module.

  • If you configure four T1, E1, or serial cables (over 1.544 M) at the same time in Cisco 2600XM series routers, you cannot turn on the data-protection and payload compression features. Also, in framed mode (channelized), you can use up to 60 channels without the data protection and payload compression features on Cisco 2600XM series routers. However, you can turn on the data protection and payload compression feature in one T1/E1.

  • There is a limitation on the data protection and payload compression features on Cisco 3660 routers. If you configure four T1, E1, or serial cables on Cisco 3660 routers, you can turn on data protection for up to two T1/E1s. In framed mode, you can use 88 channels.

Information About Circuit Emulation over IP

Circuit Emulation over IP

Circuit emulation is an end-to-end service that allows Layer 1 data to be transported transparently through an IP network. Applications that require circuit emulation need the network to provide a constant rate bit stream.

Configuration Circuit Emulation (CEM) can be configured in unidirectional mode using the emulation-mode option. Once configured, traffic will flow only in that direction through the CEM channel. When one direction of CEM traffic is detected on that channel, the CEM channel is considered to be active and a new status of the CEM channel is created to reflect the uni-directional channel.

CEoIP may use adaptive clocking as a means of synchronizing the clock frequencies at the two endpoints. Channel associated signaling (CAS) transport is provided as an optional feature to allow channelized voice applications. Payload compression is provided as an optional feature to improve bandwidth efficiency and data protection is provided to reduce the probability of data loss.

CEoIP software supports the following network modules:

  • The NM-CEM-4SER, a network module with four serial ports. To configure CEoIP software for the NM-CEM-4SER, you must configure the options of the ports. Options include dejitter buffer, payload compression, and payload size.

  • The NM-CEM-4TE1, a network module with four ports that you can configure as T1 or E1 (where all four ports support the same interface type). To configure CEoIP software for the NM-CEM-TE1, you must define the card type and then configure the options of the port.

Benefits of CEM over IP

CEoIP provides a simple migration path to IP-only networks. Examples of solutions that CEoIP integrates with IP include the following:

  • Legacy data services

  • Legacy video applications

  • Satellite data streams

  • Radar data streams

  • Telemetry for automated industrial environments (for example, power distribution)

  • Crypto tunneling for multilevel security

Adaptive Clocking for CEoIP

The adaptive clocking option of CEoIP allows the egress clock to vary by expanding or contracting the clock period from the nominal clock. After you have implemented the clocking feature, the adaptive clocking circuits continuously adjust the selected clock based on the data buffer level. You can implement adaptive clocking on each port independently.

Clock Switchover

The clock switchover option allows you to switch the clock source over to the internal clock. The switchover ensures continuity of the CEM channel when disruption in receiving the clock from the customer premises equipment (CPE) occurs. To specify the input lead state change that triggers the clock switching over from line to internal or from internal to line, use this option in Data Circuit Terminating Equipment (DCE) split mode.

Payload Compression for CEoIP

The payload compression option minimizes the amount of bandwidth that traffic consumes. It compresses the transmission of any repetitive data pattern (for example, idle code, HDLC flags, and so on) to increase the efficiency of the solution across the network.

With CEoIP software, you can adjust the size (in bytes) of the payload for the IP packet to configure efficiency as opposed to packetization. Larger payloads provide more efficiency but increase the delay. With smaller packets the overhead of the header increases. Payload compression is disabled by default.

Data Protection (Sample Repetition)

The data protection option, also known as sample repetition, reduces the probability of errors due to packet loss by sending each sample twice, in two different IP packets. Data protection consumes more bandwidth than standard transmission, but you can minimize the amount of traffic with payload compression. This feature is disabled by default.

Dejitter

The dejitter buffer size determines the ability of the emulated circuit to tolerate network jitter. The dejitter buffer in CEoIP software is configurable up to 500 milliseconds; the maximum amount of network jitter that CEoIP can tolerate is ±250 milliseconds.

Idle Pattern

The idle pattern option specifies the idle pattern to transmit when the circuit goes down. You can specify a maximum of 64 bits with two 32-bit patterns for the NM-CEM-4SER and 8-bit patterns for the NM-CEM-4TE1.

Payload Size

Payload size is the number of bytes put into each IP packet. This parameter impacts packetization delay and efficiency. Configure a high payload size to increase packetization delay and efficiency. A smaller payload size reduces packetization delay and efficiency.

Signaling for CEoIP

CEoIP software supports the transport of channel associated signaling (CAS) bits in channelized T1/E1 mode. This option extracts incremental signaling information and sends that information in separate packets.

Control Lead Configurations

CEoIP software supports the monitoring and transport of serial interface control leads.

How to Configure Circuit Emulation over IP

Configuring the NM-CEM-4TE1 Card Type

Perform this task to configure the card type for an NM-CEM-4TE1.

This task does not apply to the NM-CEM-4SER.

SUMMARY STEPS

    1.    enable

    2.    configure terminal

    3.    card type {t1 | e1} slot


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 card type {t1 | e1} slot


    Example:
    Router(config)# card type t1 1
     

    Configures the card type by specifying the transmission mode for the ports on the network module.

    • All four ports on the CEoIP T1/E1 network module must operate in the same mode.

    • Use the t1 or e1 keyword to specify the transmission mode for all four ports.

    Note   

    This command is only entered once and changes do not take effect unless the reload command is used, or the router is rebooted.

     

    What to Do Next

    Go to the Configuring the T1 E1 Line to continue configuring CEoIP on an NM-CEM-4TE1.

    Configuring the T1 E1 Line

    Perform this task to configure the T1 or E1 line, starting in global configuration mode.

    This task does not apply to the NM-CEM-4SER.

    SUMMARY STEPS

      1.    controller {t1 | e1} slot / port

      2.    Do one of the following:

      • framing {esf | sf | unframed}
      • framing {crc4 | no-crc4 | unframed}

      3.    clock source {internal | line| adaptive channel-number}

      4.    cablelength {long | short} {attenuation| length}

      5.    crc-threshold value

      6.    description text

      7.    loopback {local {line | payload}| network}


    DETAILED STEPS
       Command or ActionPurpose
      Step 1 controller {t1 | e1} slot / port


      Example:
      Router(config)# controller t1 1/0
       

      Enters controller configuration mode.

      • Use the slotand port arguments to specify the slot number and port number to be configured.

       
      Step 2Do one of the following:
      • framing {esf | sf | unframed}
      • framing {crc4 | no-crc4 | unframed}


      Example:
      Router(config-controller)# framing esf


      Example:
      Router(config-controller)# framing crc4
       

      (Optional) Configures the framing format for a T1 or E1 port to synchronize the port and the attached device.

      T1 port framing options:

      • Use the esf keyword to specify Extended Superframe as the T1 framing type.

      • Use the sf keyword to specify the Superframe (also commonly called D4 framing) as the T1 framing type. This is the default.

      E1 port framing options:

      • Use the crc4 keyword to specify the G.704 standard with optional CRC4 mechanism defined in timeslot zero (0) enabled as the E1 framing type. This is the default.

      • Use the no-crc4 keyword to specify the G.704 standard with optional CRC4 mechanism defined in timeslot zero (0) disabled as the E1 framing type.

      T1 or E1 port framing options:

      • Use the unframed keyword to specify the unchannelized mode of framing.

      Note   

      If you do not configure framing, the framing on the customer premises equipment (CPE) devices on each end of the connection must match.

       
      Step 3 clock source {internal | line| adaptive channel-number}


      Example:
      Router(config-controller)# clock source adaptive 6
       

      Configures the clock source for a T1 or E1 port.

      • Use the internal keyword to specify that the port transmit clock is derived from the time-division multiplexing (TDM) bus backplane clock, if one exists in the router, or the on-board oscillator on the network module.

      • Use the line keyword to specify that the port transmit clock is derived from the the receive clock on the same port.

      • Use the adaptive keyword to specify that the port transmit clock is locally synthesized based on the average data content of the dejitter buffer of one of the channels on this port.

      • If the adaptive keyword is selected, use the channel-number argument to specify the channel whose dejitter buffer is to be used to synthesize the transmit clock of the port.

       
      Step 4 cablelength {long | short} {attenuation| length}


      Example:
      Router(config-controller)# cablelength long -15db
       

      (Optional) Specifies the line build-out characteristics of the internal CSU on a T1 port.

      • Use the long keyword to specify that the signal characteristics are set for a long cable length.

      • Use the short keyword to specify that the signal characteristics are set for a short cable length.

      • If the long keyword is selected, use the attenuation argument to specify the T1 signal attenuation.

      • If the short keyword is selected, use the length argument to specify the T1 cable length.

      Note   

      This command does not apply to an E1 port.

       
      Step 5 crc-threshold value


      Example:
      Router(config-controller)# crc-threshold 512
       

      (Optional) Configures the number of cyclical redundancy check (CRC) errors in one second that results in the second being declared as a Severely Errored Second (SES).

      • Use the value argument to specify the number of CRC errors. Default is 320.

      Note   

      This command does not apply to an E1 port.

       
      Step 6 description text


      Example:
      Router(config-controller)# description T1 line to 3rd floor PBX
       

      (Optional) Specifies a text description of the port.

       
      Step 7 loopback {local {line | payload}| network}


      Example:
      Router(config-controller)# loopback network
       

      (Optional) Creates a loopback from a T1 or E1 port.

      • Use the local keyword to create a loopback where the information from a locally-attached CPE is transmitted back to the locally-attached CPE.

      • Use the network keyword to create a loopback where the data received over the network from a remotely-attached CPE is transmitted back to the remotely-attached CPE.

      • If the local keyword is selected, use the line keyword to create a full physical layer loopback of all bits, including data and framing.

      • If the local keyword is selected, use the payload keyword to create a loopback of the data in the individual timeslots only. In this mode, framing bits are terminated on entry and regenerated on exit instead of being looped back. This mode is not available if the port is configured for framing unframed.

       

      What to Do Next

      Go to the Creating CEM Channels on the T1 E1 Line to continue configuring CEoIP on an NM-CEM-4TE1

      Creating CEM Channels on the T1 E1 Line

      Perform this task to create CEM channels on the T1 or E1 line, starting in controller configuration mode.

      This task does not apply to the NM-CEM-4SER.

      SUMMARY STEPS

        1.    cem-group group-number {unframed| timeslots timeslot [speed {56| 64}]}

        2.    exit


      DETAILED STEPS
         Command or ActionPurpose
        Step 1 cem-group group-number {unframed| timeslots timeslot [speed {56| 64}]}


        Example:
        Router(config-controller)# cem-group 6 timeslots 1-4,9,10 speed 64
         

        Creates a circuit emulation channel from one or more timeslots of a T1 or E1 line of an NM-CEM-4TE1.

        • The group-number keyword identifies the channel number to be used for this channel. For T1 ports, the range is 0-23. For E1 ports, the range is 0-30.

        • Use the unframed keyword to specify that a single CEM channel is being created including all timeslots and the framing structure of the line.

        • Use the timeslots keyword and the timeslot-rangeargument to specify the timeslots to be included in the CEM channel. The list of timeslots may include commas and hyphens with no spaces between the numbers, commas, and hyphens.

        • Use the speed keyword to specify the speed of the channels by specifying the number of bits of each timeslot to be used. This keyword applies only to T1 channels.

         
        Step 2 exit


        Example:
        Router(config-controller)# exit


        Example:
        Router(config)#
         

        Exits controller configuration mode and returns to global configuration mode.

         

        What to Do Next

        Go to the Configuring the Connection Using the xconnect Command to continue configuring CEoIP on an NM-CEM-4TE1

        Configuring the Connection Using the xconnect Command

        Perform this task to create a connection using the xconnect command, starting in global configuration mode. This task applies to configuring CEoIP on both the NM-CEM-4TE1 and the NM-CEM-4SER.


        Note


        To properly configure the CEoIP feature, two CEoIP network modules must use the same UDP port number to communicate.


        SUMMARY STEPS

          1.    cem slot / port / cem-group

          2.    xconnect remote-ip-address virtual-connect-ID encapsulation encapsulation-type

          3.    local ip address local-ip-address

          4.    local udp port udp-port

          5.    remote udp port udp-port

          6.    exit


        DETAILED STEPS
           Command or ActionPurpose
          Step 1 cem slot / port / cem-group


          Example:
          Router(config)# cem 3/1/0
           

          Enters CEM configuration mode to configure CEM channels.

          • Use the slot argument to specify the slot number in which the network module is installed.

          • Use the port argument to specify the port number of the CEM channel to be configured.

          • Use the channel argument to specify the CEM channel number to be configured. For a serial channel enter zero. For a T1 or E1 channel enter the channel number defined in the cem-group command (see the Creating CEM Channels on the T1 E1 Line).

           
          Step 2 xconnect remote-ip-address virtual-connect-ID encapsulation encapsulation-type


          Example:
          Router(config-cem)# xconnect 10.2.0.1 0 encapsulation udp
           

          Creates one end of a connection between two CEM network modules and enters xconnect configuration mode.

          • Use the remote-ip-address argument to specify the IP address of an interface--regular or loopback--on the destination router.

          • Set the virtual-connect-ID argument to be zero.

          Note   

          Currently the only supported encapsulation type is UDP.

           
          Step 3 local ip address local-ip-address


          Example:
          Router(config-cem-xconnect)# local ip-address 10.2.0.2 
           

          Configures the IP address of an interface--regular or loopback--on the source router.

          Note   

          The local IP address must be the same as the remote IP address (at the other side) configured in the xconnect command.

           
          Step 4 local udp port udp-port


          Example:
          Router(config-cem-xconnect)# local udp port 15901
           

          Specifies the User Datagram Protocol (UDP) port number of the local CEM channel.

          Note   

          The local UDP port of a CEM channel must be the same as the remote UDP port of the CEM channel at the other end of the connection.

           
          Step 5 remote udp port udp-port


          Example:
          Router(config-cem-xconnect)# remote udp port 15902
           

          Specifies the UDP port number of the remote CEM channel.

          Note   

          The remote UDP port of a CEM channel must be the same as the local UDP port of the CEM channel at the other end of the connection.

           
          Step 6 exit


          Example:
          Router(config-cem-xconnect)# exit


          Example:
          Router(config-cem)#
           

          Exits xconnect configuration mode and returns to CEM configuration mode.

          • Repeat this command if you wish to exit CEM configuration mode return to global configuration mode.

           

          What to Do Next

          This task must be repeated on the other CEM network module and each end of the CEM connection must be configured identically to allow traffic to pass between the network modules. When both network modules have been configured, continue to the Configuring the CEM Channel.

          Configuring the CEM Channel

          Perform this task to configure the CEM T1/E1 or serial channel, starting in CEM configuration mode.

          SUMMARY STEPS

            1.    clock rate rate

            2.    clock mode {normal | split}

            3.    clock source {internal | loop| adaptive}

            4.    payload-size size

            5.    dejitter-buffer size

            6.    control-lead sampling-rate rate

            7.    control-lead state {active | fail} output-lead{on| off| follow} [{local | remote} input-lead]

            8.    data-strobe input-lead {on| off}

            9.    Cisco NM-CEM-4SER:

            10.    signaling

            11.    payload-compression

            12.    data-protection

            13.    ip dscp dscp

            14.    ip tos tos

            15.    ip precedence precedence

            16.    loopback {local | network}

            17.    exit


          DETAILED STEPS
             Command or ActionPurpose
            Step 1 clock rate rate


            Example:
            Router(config-cem)# clock rate 38400
             

            (Optional) For serial channels only. Specifies the nominal bit rate of a serial CEM channel.

            • Use the rate argument to specify the data rate of the channel in bps. Default is 64000.

             
            Step 2 clock mode {normal | split}


            Example:
            Router(config-cem)# clock mode split
             

            (Optional) For serial channels only. Specifies the clock mode of a serial CEM channel.

            • Use the normal keyword to specify that the Data Circuit-terminating Equipment (DCE) provides both the Receive Clock (RxC) and the Transmit clock (TxC) to the attached Data Terminal Equipment (DTE).

            • Use the split keyword to specify that the DCE provides the Receive Clock (RxC) to the attached DTE, and the DTE provides the external Transmit Clock (XTC or TT) to the DCE.

            Note   

            Depending on the serial cable attached to the port, the port is automatically configured as either a DCE or DTE.

             
            Step 3 clock source {internal | loop| adaptive}


            Example:
            Router(config-cem)# clock source loop
             

            (Optional) Configures the clock source for a serial CEM channel.

            • This step applies only to configuring serial channels. For information about configuring the clock source for T1 or E1 ports, see the Configuring the T1 E1 Line.

            • Use the internal keyword to specify that the clock(s) provided by the network module to the CPE is derived from the TDM bus backplane clock, if one exists in the router, or the on-board oscillator on the network module.

            • Use the loop keyword to specify that the clock provided by the network module to the CPE is derived from the the clock receive from the CPE on the same port.

            • Use the adaptive keyword to specify that the clock(s) provided by the network module to the CPE is locally synthesized based on the average data content of the local dejitter buffer.

            Note   

            The loop keyword is valid only when the clock mode split command is configured.

             
            Step 4 payload-size size


            Example:
            Router(config-cem)# payload-size 512
             

            (Optional) Specifies the number of bytes encapsulated into a single IP packet.

            • Use the size argument to specify the number of bytes included in the payload of each packet. Default is 32 bytes for a serial CEM channel.

            • For more information about T1 and E1 default values, see the payload-size command in the "Command Reference" section.

             
            Step 5 dejitter-buffer size


            Example:
            Router(config-cem)# dejitter-buffer 80
             

            (Optional) Specifies the size of the dejitter buffer used to compensate for the network filter.

            • Use the size argument to specify the size of the buffer in milliseconds. Default is 60.

             
            Step 6 control-lead sampling-rate rate


            Example:
            Router(config-cem)# control-lead sampling-rate 10
             

            (Optional) Specifies the sampling rate of input control leads on a serial CEM channel.

            • This command is used only on serial channels.

            • Use the rate argument to specify the frequency with which the control leads are sampled, in samples per second. Default is 0.

            Note   

            Control lead update packets are independent of the data packets from the same channel.

             
            Step 7 control-lead state {active | fail} output-lead{on| off| follow} [{local | remote} input-lead]


            Example:
            Router(config-cem)# control-lead state active rts follow remote cts
             

            (Optional) Specifies the state of each output control lead on a serial CEM channel.

            • This command is used only on serial channels.

            • Use the active keyword to specify the state of the control lead when the connection is active.

            • Use the fail keyword to specify the state of the control lead when the connection has failed.

            • Use the output-leadargument to specify the name of the control lead.

            • Use the on keyword to specify that the control lead is permanently asserted.

            • Use the off keyword to specify that the control lead is permanently not asserted.

            • Use the follow keyword to specify that the control lead is to follow any changes in the state of an input control lead specified by the local or remote keywords and the input-lead argument.

            • Use the input-lead argument to specify the name of the local or remote control lead to follow.

            Note   

            Control lead update packets are independent of the data packets for the same channel.

            Note   

            The control-lead sampling-rate parameter must be set to non-zero for this feature to operate.

             
            Step 8 data-strobe input-lead {on| off}


            Example:
            Router(config-cem)# data-strobe dtr on
             

            (Optional) Specifies that an input control lead is to be monitored and data is packetized and sent only when the specified control lead is in the specified state.

            • This command is used only on serial channels.

            • Use the input-lead argument to specify the input control lead to be monitored to determine whether input data is to be packetized.

            • Use the on keyword to specify that data packets are to be sent from this CEM channel only when the specified input lead is asserted.

            • Use the off keyword to specify that data packets are to be sent from this CEM channel only when the specified input lead is not asserted.

            • Use this command to save bandwidth when the attached CPE is inactive.

            Note   

            Control lead update packets are still sent even if data packets are withheld.

             
            Step 9 Cisco NM-CEM-4SER:


            Example:
                        
                          idle-pattern
                         length pattern1 [pattern2]


            Example:
                        
                          
                            Cisco NM-CEM-4TE1:
                        
                      


            Example:
                        
                          idle-pattern
                         pattern1


            Example:
                        
                          
                            Cisco NM-CEM-4SER:
                        
                      


            Example:
            Router(config-cem)# idle-pattern 53 0x12345678   0x87654321


            Example:
                        
                          
                            Cisco NM-CEM-4TE1:
                        
                      


            Example:
            Router(config-cem)# idle-pattern 0x66
             

            (Optional) Defines the idle data pattern to send to the attached CPE when packets are lost or the de-jitter buffer experiences an under-run condition.

            For serial CEM channels:

            • A bit pattern up to 64 bits long may be specified.

            • Use the pattern1 argument to specify up to 32 bits of the least significant bits of the idle data pattern, in hex notation. Default is 0xFF.

            • Use the pattern2 argument to specify the most significant bits of the idle data pattern, in hex notation. If the length argument is 32 bits or less, this argument is not permitted.

            • Use the length argument to specify the total length of the repeating bit pattern. Default is 8 bits.

            For T1 or E1 CEM channels:

            • An eight-bit pattern is specified.

             
            Step 10 signaling


            Example:
            Router(config-cem)# signaling
             

            (Optional) Enables the transport of Channel Associated Signaling (CAS) bits.

            Note   

            This command applies only to framed T1 or E1 data channels.

             
            Step 11 payload-compression


            Example:
            Router(config-cem)# payload-compression
             

            (Optional) Enables payload compression on a CEM channel.

            Note   

            Enabling payload compression adds a delay equal to one packet time.

             
            Step 12 data-protection


            Example:
            Router(config-cem)# data-protection
             

            (Optional) Enables data protection by transmitting each data bit twice, once in each of two consecutive data packets.

            • Use the data-protection command to protect transmissions from the effects of lost IP packets.

            Caution   

            Use this command carefully because it increases the network bandwidth used by the CEM connection.

             
            Step 13 ip dscp dscp


            Example:
            Router(config-cem)# ip dscp 36
             

            (Optional) Configures the IP Differentiated Service Code Point (DSCP) for packets originating from this CEM channel.

            • Use the dscp argument to specify the value placed in the DSCP field of IP packets originating from this channel. Default is 46.

            Note   

            If DSCP is configured, the ip tos and ip precedence commands are not available because they are mutually exclusive.

             
            Step 14 ip tos tos


            Example:
            Router(config-cem)# ip tos 11
             

            (Optional) Configures the IP type of service (ToS) bits for the CEM channel.

            • Use the tos argument to specify the value placed in the ToS field of IP packets originating from this channel. Default is 5.

            Note   

            If DSCP is configured, the ip tos command is not available because they are mutually exclusive.

             
            Step 15 ip precedence precedence


            Example:
            Router(config-cem)# ip precedence 7
             

            (Optional) Configures the IP precedence bits for the CEM channel.

            • Use the precedence argument to specify the value placed in the precedence field of IP packets originating from this channel. Default is 0.

            Note   

            If DSCP is configured, the ip precedence command is not available because they are mutually exclusive.

             
            Step 16 loopback {local | network}


            Example:
            Router(config-cem)# loopback network
             

            (Optional) Creates a loopback from a CEM serial channel.

            • Use the local keyword to create a loopback where the information from a locally-attached CPE is transmitted back to the locally-attached CPE.

            • Use the network keyword to create a loopback where the data received over the network from a remotely-attached CPE is transmitted back to the remotely-attached CPE.

            Note   

            For configuring a loopback on a T1 or E1 port, see the Creating CEM Channels on the T1 E1 Line.

             
            Step 17 exit


            Example:
            Router(config-cem)# exit
             

            Exits CEM configuration mode and returns to global configuration mode.

            • Use this command one more time to exit to privileged EXEC mode.

             

            What to Do Next

            Configuration Examples for CEoIP

            Configuring a T1 CEM Network Module Example

            The following example shows a basic configuration of a T1 network module to configure the CEoIP feature.

            card type t1 0
            controller t1 4/0
             cem-group 6 timeslots 1-4,9,10 speed 64
             framing esf
             linecode b8zs
             clock source adaptive 6
             cablelength long -15db
             crc-threshold 512
             description T1 line to 3rd floor PBX
             loopback network
             no shutdown
             exit
            cem 2/1/6
             xconnect 10.2.0.1 0 encapsulation udp
             local ip-address 10.2.0.9 
             local udp port 15901
             remote udp port 15901
             payload-size 512
             dejitter-buffer 80
             signaling
            exit

            Additional References

            For additional information related to the CEoIP feature, refer to the following references:

            Related Documents

            Related Topic

            Document Title

            CEoIP NMs

            Release Notes for Cisco NM-CEM-4TE1 and NM-CEM-4SER Network Module Software

            Standards

            Standards

            Title

            GR-1089

            Electromagnetic Compatibility and Electrical Safety - Generic Criteria for Network Telecommunications Equipment

            GR-63

            Network Equipment-Building System (NEBS) Requirements: Physical Protection

            TIA/EIA-IS-968

            Technical Requirements for Connection of Terminal Equipment to the Telephone Network

            MIBs

            MIBs

            MIBs Link

            • OLD-CISCO-CHASSIS-MIB

            • RFC1406-MIB

            • CISCO-ENTITY-VENDORTYPE-OID-MIB

            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

            RFCs

            RFCs

            Title

            RFC 1406

            Definitions of Managed Objects for the DS1 and E1 Interface Types

            RFC 2495

            Definitions of Managed Objects for the DS1, E1, DS2 and E2 Interface Types

            Note   

            CEoIP supports RFC2495 to the same extent as IOS supports this RFC.

            Technical Assistance

            Description

            Link

            Technical Assistance Center (TAC) home page, containing 30,000 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/​public/​support/​tac/​home.shtml

            Command Reference

            The following commands are introduced or modified in the feature or features documented in this module. For information about these commands, see the Cisco IOS Interface and Hardware Component Command Reference at http://www.cisco.com/en/US/docs/ios/interface/command/reference/ir_book.html. For information about all Cisco IOS commands, go to the Command Lookup Tool at http://tools.cisco.com/Support/CLILookup or to the Cisco IOS Master Commands List .

            • cem

            • cem-group

            • clear cem

            • clock mode

            • clock source (CEM)

            • clock-switchover

            • control-lead sampling-rate

            • control-lead state

            • crc-threshold

            • data-protection

            • data-strobe

            • default (CEM)

            • dejitter-buffer

            • emulation-mode

            • framing (CEM)

            • idle-pattern

            • ip dscp

            • local ip address

            • local udp port

            • loopback (CEM)

            • payload-compression

            • payload-size

            • remote udp port

            • show cem

            • signaling

            • xconnect (CEM)

            Feature Information for Circuit Emulation over IP

            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.

            Release

            Modification

            12.3(7)T

            This feature was introduced.

            12.2(33)SRD

            Included information on clock switchover and unidirectional emulation mode.