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Chapter 4

Introduction to the Cisco IOS

Connecting to a Cisco Router

You can connect to a Cisco router to configure the router, verify the config-
uration, and check statistics. There are different ways to do this, but most
often, the first place you would connect to is the console port. The

console

port

is usually an RJ-45 connection located at the back of the router; by

default, there's no password set.

See Chapter 1 for an explanation on how to configure a PC to connect to a

router console port.

But you can also connect to a Cisco router through an

auxiliary port

which is really the same thing as a console port so you can use it as one.
However, this auxiliary port also allows you to configure modem commands
so a modem can be connected to the router. This is a cool feature that allows
you to dial up a remote router and attach to the auxiliary port if the router
is down and you need to configure it.

The third way to connect to a Cisco router is through the program

Telnet

Telnet is a terminal emulation program that acts as though it's a dumb-
terminal. You can then use Telnet to connect to any active interface on a
router like an Ethernet or serial port.

Figure 4.1 shows an illustration of a 2501 Cisco router. Pay special atten-

tion to all the different kinds of interfaces and connections.

F I G U R E 4 . 1

A Cisco 2501 router

The 2501 router has two serial interfaces for WAN connection and one

Attachment Unit Interface (AUI) connection for a 10Mbps Ethernet network
connection. This router also has one console and one auxiliary connection
via RJ-45 connectors.

Bringing Up a Router

So let's get started! When you first bring up a Cisco router, it will run a
power-on self-test (POST), and if that passes, it will then look for and load

AUI

SERIAL 0

SERIAL 1

CONSOLE

AUX

CISCO 2501

Input: 100-240VAC

Freq: 50.60 Hz

Current: 1.2-0.6A

Watts: 40W

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