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Configure a Cisco Router as Terminal Server

     Introduction
     Requirements
     Configure the router as Terminal server
     Next Step
     Troubleshoot the Procedure
     Related Information

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Introduction

This document explains how to configure a Cisco router as a terminal server. A terminal is used to provide out-of-band management access to various devices.

A terminal server acts as a single access point to configure other devices using CLI. For a router to act as a terminal server it must have multiple, low speed, asynchronous ports. Asynchronous ports are 68 pin ports and use a CAB-OCTAL-ASYNC cable, which provides an eight RJ-45 rolled cable asynchronous ports, to connect to the console port of other devices. Each RJ-45 rolled cable asynchronous port can be used to connect to the console of any device; and thus one asynchronous 68 pin port on the router serves for connecting to the console of upto eight devices. If you have more than eight devices you need one more CAB-OCTAL-ASYNC cable and connect it to the second 68 pin asynchronous port on the router. This can serve for upto sixteen devices.

In this example, a loopback interface on the router was configured and assigned a free IP address from the LAN Addressing Worksheet. This is a recommended configuration since a loopback interface always remains up and the connectivity to the loopback IP address gets established which could be used to connect to other devices. However, any configured IP address on the router could be used. But, for some reason if the associated interface goes down, the connectivity to the interface IP address is lost likewise for the other devices.

Requirements

To perform the steps described in this document, you need to have these items:

Complete the initial configuration in Configure Your Router with Security Device Manager document.
A router with asynchronous serial port and CAB-OCTAL-ASYNC cable to connect to the asynchronous port.

Configure the router as Terminal server

Follow these steps to configure a router as terminal server:

Complete these steps:

Open a web browser and type http://router IP address in the Address field. The router's IP address is the IP address that you entered in the LAN Addressing Worksheet (L6A).

Note: For further information on how to launch SDM, refer to Configure Your Router with Security Device Manager.
Click Tools and select Configuration Management.
Select Configuration Management > Config Editor.
Click I Agree to save the running configuration and to launch Config Editor.
In the Edit configuration window:

Enter these values to create a loopback address:
- interface loopback 0
- ip address 192.168.12.1 255.255.255.0
- exit
Enter these values to configure port mapping to other devices:
- ip host R1 2001 192.168.12.1
- ip host R2 2002 192.168.12.1
- ip host R3 2003 192.168.12.1
- ip host pix 2004 192.168.12.1
- ip host Sw1 2005 192.168.12.1
- ip host Sw2 2006 192.168.12.1
- ip host AP1 2007 192.168.12.1
- ip host AP2 2008 192.168.12.1
Note: The commands mean that R1’s console is connected using the first RJ-45 cable and is available on port 2001, R2’s console is connected using the second RJ-45 cable and is available on port 2002 and so on. Remember that the ports are numbered as 2000 plus the line number. Hence, the first port is 2001. If you have more than eight devices and have connected a second CAB-OCTAL-ASYNC cable then you need to add a similar configuration line with the port numbers starting from 2009 till 2016.

Enter these to configure the line for asynchronous ports:
- line 1 8
- no exec
- transport input all
- exec-timeout 2 30
  
  Note: The line command is used to configure the properties of the asynchronous ports. If you have connected two CAB-OCTAL-ASYNC cables then you must change the last port to 16 and your line command would be “line 1 16”. The exec-timeout command defines the inactivity time after which the line is set free. In this example inactivity timeout is 2 mins and 30 secs.
Click Merge with Running Config.
Click Yes in the SDM warning window.
You get the confirmation message once the commands are delivered and merged to the running configuration.
Click Save to save the running configuration to flash.

Next Step

You have now configured your router as a Terminal server.

To connect to the console of a device, telnet to the terminal server router’s loopback address and specify the port number associated to the device. For example, to connect to console of router R1 (from our example) type telnet 192.168.12.1 2001 in the Run dialog box from your PC.

To make further changes to your router, refer to the Router Support Page.

To configure other devices in your network, refer to the Configuration Overview Page.

Troubleshoot the Procedure

This section provides information about the common problems that you may encounter. If this information does not solve your problem, contact the SMB Technical Assistance Center (SMB TAC) for assistance.

Problem	Cause(s) and Suggested Solution(s)
You get authentication failure.	Verify whether AAA is configured correctly on both the terminal server and the connecting device and remember that the terminal server performs the first authentication (if configured), while the device to which you try to connect performs the second authentication (if configured).
You are unable to connect to the device on the configured port.	Check if you are trying to connect to the correct port and that the cable is connected to the console of the device.