Configuring an E3 Interface

To configure properties on an E3 interface:

  1. From the Configure Interfaces page, as shown in Figure 1, select the E3 interface you want to configure.

    The properties you can configure on an E3 interface are displayed, as shown in Figure 3.

    Figure 3: E3 Interfaces Configuration Page

    E3 Interfaces Configuration Page
  2. Enter information into the Configure Interfaces page, as described in Table 6.
  3. Click one of the following buttons:
    • To apply the configuration and return to the configuration page that lists all interfaces, click OK.
    • To cancel your entries and return to the Configure Interfaces page, click Cancel.

Table 6: E3 Configuration Summary



Your Action

Logical Interfaces

Add logical interfaces

Defines one or more logical units that you connect to this physical E3 interface. You must define at least one logical unit for an E3 interface. You can define multiple units if the encapsulation type is Frame Relay.

Click Add.

Logical Interface Description

(Optional) Describes the logical interface.

Type a text description of the logical interface to more clearly identify it in monitoring displays.

IPv4 Addresses and Prefixes

Specifies one or more IPv4 addresses for the interface.

  1. Click Add.
  2. Type one or more IPv4 addresses and prefixes. For example:

  3. Click OK.

Physical Interface Description

(Optional) Adds supplementary information about the physical E3 interface.

Type a text description of the E3 interface to more clearly identify it in monitoring displays.

MTU (bytes)

Specifies the maximum transmission unit size for the E3 interface.

Type a value between 256 and 9192 bytes. The default MTU for E3 interfaces is 4474.


Specifies the transmit clock source for the E3 line.

From the list, select one of the following:

  • internal—Device's own system clock (the default)
  • external—Clock received from the E3 interface


Specifies the encapsulation type for traffic on the interface.

From the list, select the encapsulation for this E3 interface:

  • PPP
  • Frame Relay
  • Cisco HDLC

Enable CHAP

Enables or disables CHAP authentication on an E3 interface with PPP encapsulation only.

  • To enable CHAP, select the check box.
  • To disable CHAP, clear the check box.
CHAP Local Identity (available if CHAP is enabled)

Use System Host Name

Specifies that the E3 interface uses the device's system hostname in CHAP challenge and response packets.

  • To enable, select the check box (the default).
  • To disable, clear the check box.

Local Name

If Use System Host Name is disabled, specifies the local name for CHAP to use.

Type a local name for this E3 interface.

CHAP Peer Identity

Identifies the client or peer with which the device communicates on this E3 interface.

Type the CHAP client name.

CHAP Secret

Specifies the secret password for CHAP authentication, known to both sides of the connection.

Type a password that is known to the other side of the connection. Use a combination of letters and numbers that is difficult for others to guess.

E3 Options

Bert Algorithm

Specifies the bit error rate test (BERT) algorithm to use during a BERT.

BERT is supported only when transmission is unframed. (See the Unframed option.)

From the Bert Algorithm list, select the algorithm to use:

  • all-ones-repeating
  • alternating-ones-zeros
  • all-zeros-repeating
  • pseudo-2e11–o152
  • pseudo-2e15–o151
  • pseudo-2e20–o151
  • pseudo-2e20–o153
  • pseudo-2e23–o151
  • pseudo-2e29
  • pseudo-2e31
  • pseudo-2e9–o153

The default is pseudo-2e15-o151.

Bert Error Rate

Specifies the exponent n in the bit error rate 10–n.

Type a value between 3 and 7, or 0. For example, a value of 6 specifies that 1 bit out of 1,000,000 is transmitted in error. The default is 0 (no bits are transmitted in error).

Bert Period

Specifies the length of time, in seconds, of the BERT.

Type a value between 1 and 240. The default is 10.

Compatibility Mode

Defines the transmission mode and subrating to use on the E3 interface. The mode must be set to the type of channel service unit (CSU) connected to the interface. The subrating specified must be the same subrating configured on the CSU.

CSU compatibility mode and subrating are supported only when transmission is unframed. (See the Unframed option.)

Select one of the following check boxes:

  • Off—CSU compatibility is disabled.
  • Digital-Link—Compatible with a Digital Link CSU.
  • Kentrox—Compatible with a Kentrox CSU.

If you select Digital-Link, you can optionally specify a subrate by selecting a value from the Subrate list.

If you select Kentrox, you can optionally specify a subrate by typing a value from 1 through 48 in the Subrate box.

If you do not specify a subrate, the full E3 rate is used.

Frame Checksum

Specifies the number of bits in the frame checksum. A 32-bit checksum provides more reliable packet verification, but is not supported by some older equipment.

From the Frame Checksum list, select 16 or 32. The default value is 16.

Idle Cycle Flag

Specifies the value to transmit during idle cycles.

From the Idle Cycle Flag list, select one of the following:

  • flags—Transmits the value 0x7E during idle cycles. This is the default.
  • ones—Transmits the value 0xFF during idle cycles.


Configures the E3 interface as a loopback interface for testing purposes.

When E3 is configured as a local loopback interface, the device transmits test traffic simultaneously to the CSU and to the receiver at the E3 interface.

When E3 is configured as a remote loopback interface, test traffic transmitted by the CSU is simultaneously received at the E3 interface and transmitted back to the CSU.

From the Loopback list, select one of the following:

  • local—Traffic loops from the transmitter to the receiver at the E3 interface during tests.
  • remote—Traffic loops from the receiver to the transmitter at the E3 interface during tests.

Payload Scrambler

Specifies whether the payload of the packet is to be scrambled or randomized when transmitted. Scrambling eliminates nonvariable bit patterns in the transmission, which can generate link-layer errors across an E3 link.

The payload scrambler is supported only when CSU compatibility is enabled and transmission is framed. (See the Compatibility Mode and Unframed options.)

Select one of the following check boxes:

  • Yes—Transmission is scrambled.
  • No—Transmission is not scrambled.

Start End Flag

Specifies whether the end and start flags are separated.

From the Start End Flag list, select one of the following:

  • filler—Flags are separated by idle cycles.
  • shared—Flags overlap (no separation).


Specifies whether the transmission is framed (G.751 framing) or unframed.

Select one of the following check boxes:

  • Yes—Unframed transmission.
  • No—Framed transmission.