The Serial Line configuration lets you set a WAN device to asynchronous or synchronous if the device supports both line disciplines. It also lets you set HDLC or asynchronous parameters for WAN devices. This document describes the Serial Line configuration commands. It includes the following topics:

Displaying the Serial Line Configuration Prompt

Routers that have multiple serial devices display the slot number of the device that you are configuring as part of the prompt. Serial devices that have multiple ports also show the port number of the device as part of the prompt. For example, the following prompt means you are configuring a serial device in slot 2 port 3.

Serial Config <WAN2-3>

1. To see a list of devices, enter list devices at the Config> prompt. To see a list of interfaces, enter list interfaces at the Config> prompt.

2. Enter the network command to display the circuit configuration prompt. The network number is the number of a serial interface.

Config>network
What is the network number [0]? 1
Circuit Configuration
Circuit Config <NET-1>

3. Enter sl at the Circuit Config <NET-#> prompt.

Circuit Config <NET-1> sl
Serial Line Configuration

Serial Config <WAN>

Not all parameters apply to all router platforms. Press Space twice after you type a command to display the available parameters for each command. Enter help for information about using the command line interface.

[C] means the command is available at the Serial Config <WAN> prompt.

There are no monitoring commands for serial devices.

Table 1 Serial Line Commands

Command	Function
E1 [C] [M]	Displays the E1 configuration or monitoring prompt.
Exit [C]	Returns to the previous prompt.
List [C]	Lists the configuration of the serial line.
Set [C]	Configures the serial device.
T1 [C] [M]	Displays the T1 configuration or monitoring prompt.

E1 [C] [M]

Syntax: e1

E1 user configuration

E1 Config <NET-1>

Syntax: exit

Circuit Config <NET-1>

Syntax: list

Line Discipline:                  Sync
Maximum network layer frame size: 2048
Speed:                            64000
HDLC Data encoding:               NRZ
HDLC Idle State:                  Flag
Transmit delay counter:           0 units
No cable installed 

Syntax: set

async databits

async frame-size

async parity

async speed

async stopbits

hdlc cable

hdlc clocking

hdlc encoding

hdlc frame-size

hdlc idle

hdlc speed

hdlc transmit-delay

line-discipline

Example: set async databits

Data bits [8]?

Example: set async frame-size

Frame size [2048]?

Example: set async parity none

async speed 1200 or 2400 or 4800 or 9600 or 19200 or 38400 or 57600 or 115200

For 14.4k modems, set the speed to 57600.

For 28.8k modems, set the speed to 115200.

Note: For GT 250 routers, the maximum asynchronous speed is 57600.

Line speed [57600]? 

Example: set async stopbits

Stop bits [1]?

• RS-232 DTE

• RS-232 DCE

• V35 DTE

• V35 DCE

• V36

• DTE/DCE

hdlc clocking external or internal or mixed

To connect to a modem or DSU, configure clocking as external. To connect directly to another DTE device, use a DCE cable and set the clocking to internal. If the modem provides the receive clock lines and expects the transmit clock line, use mixed.

For internal and mixed clocking, use the set hdlc speed command to configure a clock speed.

For external clocking, if you want line speed reporting, set the external clock speed using the set hdlc speed command. You can display the line speed using the interface command at the + prompt or using SNMP.

Note: You cannot boot over a GTAM Quad serial device when you configure clocking as mixed.

hdlc encoding NRZ or NRZI

Example: set hdlc encoding nrz

hdlc frame-size value

Example: set hdlc frame-size

Frame Size [2048]? 

Example: set hdlc idle flag

hdlc speed bits per second

• internal, hdlc speed specifies the speed of the transmit and receive clock lines.

• mixed, hdlc speed applies to the transmit clock line only.

• external, hdlc speed provides line speed reporting via SNMP and the list interface command at the + prompt. For external clocking, setting hdlc speed to 0 (zero) causes the router to dynamically calculate an approximate speed, which it can report via SNMP and the list interface command.

Example: set hdlc speed

Clock Speed [64000]? 

For GTAM devices, sets the period of time, in microseconds, between the transmission of each frame. The range is 0 to 65535.

For all other devices, sets the number of extra flags between each frame. The range is 0 to 15.

For all platforms, the default is 0, which means the router does not insert a delay between frames.

Example: set hdlc transmit-delay

Transmit Delay Counter [0]? 

Example: set line-discipline async

T1 [C] [M]

Syntax: t1

T1 user configuration

T1 Config <NET-1>