Serial Interface Commands

This chapter describes the serial interface commands you use to configure the serial interface ports on the Cisco 3800 system. Only three commands are unique to the Cisco 3800 series for describing the physical interface layer. (See Table 8-1.)

Table  8-1: Commands to Configure the Serial Interface

Command	Description
ignore-dcd	Configure the serial interface to ignore DCD signals.
ignore-signals	Configure the serial interface to ignore input signals.
media-type	Identify the media type for the serial interface port.

Quick Reference of Serial Interface Commands and Modes

Figure 8-1 illustrates the serial interface commands with modes and prompts.

Figure 8-1: Serial Interface Commands with Modes and Prompts

ignore-dcd

Cisco 3800 system serial interfaces are DCE. By default, the serial interface monitors RTS as an indicator of lines up or down. Setting ignore-dcd causes the interface to monitor DTR instead. Using ignore-signals causes the interface to ignore both input signals, RTS and DTR, and to stay up regardless of their state.

From interface configuration mode, enter the ignore-dcd command. Use the no form of this command to use the default configuration of monitoring RTS as an indicator of lines up or down.

Europa (conf-if)# interface serial n/n ignore-dcd 
Europa (conf-if)# interface serial n/n no ignore-dcd

See the publication Cisco IOS Software Command Summary for more information about the ignore-dcd command.

Example

The following example configures serial interface 1/0 to monitor the DSR signal as the indicator of a line being up or down:

Europa (conf-if)# interface serial 1/0 ignore-dcd

Related Command

ignore-signals

ignore-signals

Use the ignore signals command to configure the serial interface to ignore input signals. By default the serial interface monitors RTS as an indicator of a line being up or down. Use the no form of this command to re-establish recognition.

Europa (conf-if)# ignore-signals
Europa (conf-if)# no ignore-signals

See the publication Cisco IOS Software Command Summary for a full description of this command. Setting ignore-dcd causes the interface to monitor DTR instead. Setting ignore-signals causes the interface to ignore both input signals, RTS and DTR, and to stay up regardless of their state.

Related Commands

ignore-dcd

media-type

The Cisco 3800 system uses custom cables. Use the media-type command to select the appropriate media type for your serial interface ports.

Europa (conf-if)# media-type { rs232 | v35 | rs422 | rs449 | eia530 }

Syntax Description

rs232	Use the RS-232/V.28 interface.
v35	Use the V.35 interface.
rs422	Use the RS-422/V.11 interface, same as X.21.
rs449	Use the RS-449 interface.
eia530	Use the EIA-530 interface.