Configuration Tasks

Configure a T3 interface by entering Global Configuration mode and performing the following tasks:

  1. Configure a T3 controller.
  2. (Optional) Configure MDL settings.
  3. (Optional) Configure other settings for the interface.
  4. Configure HDLC channels for T3 frame and E3 frame controllers.
  5. (Optional) Configure fractional T3 for T3 frame controllers.
  6. Use the appropriate show commands to verify your configuration.

E3 interface configuration tasks are identical to T3 interface configuration tasks, except that the CLI commands contain e3 instead of t3.

For example, you configure an E3 controller with the controller e3 command instead of the controller t3 command.

Configuring a T3 or an E3 Controller

To configure a T3 or an E3 controller:

  1. Select the T3 or E3 controller from Global Configuration mode.
    host1(config)#controller t3 3/2
  2. Enable the T3 or E3 controller.
    host1(config-controll)#no shutdown
  3. (CT3/T3-F0 line module only) Enable unchannelized operation for this controller.
    host1(config-controll)#no channelized


controller e3

controller t3


Configuring MDL Messages

You can configure a T3 interface to send MDL messages. MDL messages are supported only when T3 framing uses C-bit parity, the default setting.

To configure a T3 interface to send MDL messages:

  1. Specify a T3 interface.
    host1(config)#controller t3 8/0
  2. (Optional) Configure the interface to operate in an MDL carrier environment.
    host1(config-controll)#mdl carrier
  3. Specify the MDL messages.
    host1(config-controll)#mdl string eic "ERX1410" host1(config-controll)#mdl string fic "FG786" host1(config-controll)#mdl string lic “ Bldg 10" host1(config-controll)#mdl string pfi "Site 25" host1(config-controll)#mdl string port 0800
  4. Enable transmission of MDL messages.
    host1(config-controll)#mdl transmit path-id host1(config-controll)#mdl transmit idle-signal host1(config-controll)#mdl transmit test-signal

mdl carrier

mdl string

mdl transmit

Optional Tasks

The following configuration tasks are optional for T3 and E3 interfaces:


clock source





Configuring Fractional T3

You can configure fractional T3 on T3 frame interfaces. E3 frame interfaces do not support fractional E3.

Fractional T3 is a portion of a T3 transmission service and provides a set of lines with a speed that is greater than T1 (1.544 Mbps), but less than T3 (44.736 Mbps).

To configure fractional T3:

  1. Set the DSU mode for the lines.
  2. Set the speed of the fractional T3 lines.
  3. Enable scrambling of the payload.

    Caution: Complete all three steps at the same time. Otherwise, the interface might drop packets unexpectedly.

dsu bandwidth

dsu mode


Configuring an HDLC Channel

You must configure an HDLC channel for each T3 frame or E3 frame controller.

To configure an HDLC channel, configure a serial interface (for example, HDLC channel in slot 0, 1).

host1(config)#interface serial 0/1

Optional Tasks

The following configuration tasks are optional when you configure an HDLC channel on a T3/E3 frame interface:



interface serial

invert data




serial description