Terminal Server Setup.pdf

Cisco − Configuring a Terminal/Comm Server

Table of Contents

Configuring a Terminal/Comm Server. ............................................................................................................1

Introduction. ............................................................................................................................................1

Before You Begin. ..................................................................................................................................1

Conventions. .....................................................................................................................................1

Prerequisites. ....................................................................................................................................1

Components Used.. ...........................................................................................................................1

Cabling. ...................................................................................................................................................2

Design Strategy. ......................................................................................................................................2

Configure. ...............................................................................................................................................2

Network Diagram. ............................................................................................................................3

Configurations. .................................................................................................................................3

Command Summary. ........................................................................................................................5

Switching Between Active Sessions. ......................................................................................................6

Terminating Active Sessions. .................................................................................................................6

Verify and Troubleshoot. ........................................................................................................................6

Related Information. ...............................................................................................................................7

Configuring a Terminal/Comm Server

Introduction

Before You Begin

Conventions

Prerequisites

Components Used

Cabling

Design Strategy

Configure

Network Diagram

Configurations

Command Summary

Switching Between Active Sessions

Terminating Active Sessions

Verify and Troubleshoot

Related Information

Introduction

A terminal or comm server commonly provides out−of−band access for multiple devices. A terminal server is

a router with multiple, low speed, asynchronous ports that are connected to other serial devices, such as

modems or console ports on routers or switches.

The terminal server allows you to use a single point to access the console ports of many devices. Using a

terminal server avoids the need for configuring backup scenarios such as modems on auxiliary ports for every

device. You can also configure a single modem on the auxiliary port of the terminal server, thus providing

dial−up service to the other devices during a network connectivity failure.

This document shows how to configure a terminal server to access only the console ports on other routers

using Reverse Telnet. Reverse Telnet allows you to Telnet out from a device you are telnetting from, but on a

different interface. For more information on Reverse Telnet refer to Establishing a Reverse Telnet Session to a

Modem.

Before You Begin

Conventions

For more information on document conventions, see the Cisco Technical Tips Conventions.

Prerequisites

There are no specific prerequisites for this document.

Components Used

This document is not restricted to specific software and hardware versions.

Cisco − Configuring a Terminal/Comm Server

Cabling

The Cisco 2509 − 2512 series routers use a 68−pin connector and breakout cable. This cable

(CAB−OCTAL−ASYNC) provides eight RJ−45 rolled cable async ports on each 68−pin connector. You can

connect each RJ−45 rolled cable async port to the console port of a device. The 2511 allows for a maximum

of 16 devices to be remotely accessible. In addition, the NM−16A or NM−32A high density async network

modules are available for the Cisco 2600 and 3600 series routers to provide the same function. For more

information on cabling refer to the Serial Cable Guide and the Cabling Guide for RJ−45 Console and AUX

Ports.

Note: The async ports from the 68−pin connector are data terminal equipment (DTE) devices. DTE to DTE

devices require a rolled (null modem) cable and DTE to data circuit−terminating equipment (DCE) devices

require a straight−through cable. Since the CAB−OCTAL−ASYNC cable is itself rolled, you can connect

each cable directly to the console ports of devices with RJ−45 interfaces. However, if the console port of the

device you are connecting to is a 25 pin interface (DCE) use the RJ−45 to 25 pin adapter marked "Modem" (to

reverse the "roll") to complete the connection.

Port types for console and auxiliary ports on Cisco routers and switches are:

Interface Type

DB25 Interface

RJ−45 Interface

Console

DCE

DTE

AUX

DTE

Design Strategy

Configure the terminal server so that it is accessible from anywhere by giving it a registered public Internet

address, and by locating it outside the firewall so that firewall issues will not interrupt your connection. This

ensures that you can always maintain connectivity to the terminal server and have access to the connected

devices. If you are concerned about security, you may want to configure access lists to only allow access to

the terminal server from certain addresses. You can also configure server−based authentication, authorization,

and accounting (AAA) such as RADIUS or TACACS+ for a more robust security solution. For more

information on AAA refer to the Cisco AAA Implementation Case Study.

You can configure a modem on the auxiliary port of the terminal server for dial backup in the event your

primary connection (through the Internet) goes down. This eliminates the need to configure a dial backup for

each device, as the terminal server is connected through its async ports to the console ports of the other

devices. For more information on connecting a modem to the AUX port, refer to Modem−Router Connection

Guide.

Use the ip default gateway statement pointing to the the next hop router on the Internet. This allows you to

have connectivity to the terminal server through the Internet even if routing is not enabled. For example, the

terminal server is in ROM monitor (ROMMON) mode as a result of a bad reboot after a power outage.

Configure

In this section, you are presented with the information to configure the features described in this document.

Note: To find additional information on the commands used in this document, use the Command Lookup

Tool ( registered customers only ) .

Cisco − Configuring a Terminal/Comm Server

Network Diagram

This document uses the network setup shown in the diagram below.

Configurations

This document uses the configuration shown below.

Cisco 2511

aus−comm−server# show running−config

version 12.0

service timestamps debug datetime msec localtime show−timezone

service timestamps log datetime msec localtime show−timezone

service password−encryption

hostname aus−comm−server

enable secret <deleted>

username cisco password <deleted>

ip subnet−zero

ip domain−list cisco.com

no ip domain−lookup

ip host 3600−3 2014 172.21.1.1

!−−− The host 3600−3 is connected to port

!−−− 14 of the comm server.

!−−− The IP address should be that of an

!−−− interface on the comm server.

ip host 3600−2 2013 172.21.1.1

ip host 5200−1 2010 172.21.1.1

Cisco − Configuring a Terminal/Comm Server

ip host 2600−1 2008 172.21.1.1

ip host 2509−1 2007 172.21.1.1

ip host 4500−1 2015 172.21.1.1

ip host 3600−1 2012 172.21.1.1

ip host 2511−2 2002 172.21.1.1

ip host 2511−rj 2003 172.21.1.1

ip host 2511−1 2001 172.21.1.1

ip host 5200−2 2011 172.21.1.1

ip host 2520−1 2004 172.21.1.1

ip host 2520−2 2005 172.21.1.1

ip host 2600−2 2009 172.21.1.1

ip host 2513−1 2006 172.21.1.1

ip host pix−1 2016 172.21.1.1

process−max−time 200

interface Loopback1

ip address 172.21.1.1 255.0.0.0

!−−− This address was used in the IP host commands above.

!−−− Loopback interfaces are preferred since

!−−− they are virtual and are always available.

no ip directed−broadcast

interface Ethernet0

ip address 171.55.31.5 255.255.255.192

!−−− Use a public IP address to ensure that

!−−− there is connectivity.

No ip directed−broadcast

no ip mroute−cache

interface Serial0

no ip address

no ip directed−broadcast

no ip mroute−cache

shutdown

ip default−gateway 171.55.31.1

!−−− Default gateway when routing is disabled

!−−− (for example, the router is

!−−− in boot ROM mode).

ip classless

ip route 0.0.0.0 0.0.0.0 171.55.31.1

!−−− Set default route for external network.

no ip http server

line con 0

transport input all

line 1 16

session−timeout 20

!−−− Session times out after 20 minutes

!−−− of inactivity.

no exec

Cisco − Configuring a Terminal/Comm Server

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