In This Article

Routing Explained

The Cisco 2500 Series Router: A Brief Overview

Setting Up & Configuring Your Router

Further Reading

Routing Explained

You
can think of routing as mailing a letter. When you send a letter, you specify a
destination and a source address. You must take it to the Post Office (at least
where I live) and they take care of the letter from there. The post office is
your ‘Default Gateway’ to the postal network just as routers are usually the
Default Gateway in your network. At the post office, they have a list of
destinations – a Routing Table – and the ‘ports’ to send the letter out of in
order for it to arrive at the destination. From there, it gets sent out to the
appropriate destination.

The Cisco 2500 Series Router: A Brief
Overview

Though
outdated, the Cisco 2500 series router is still a very popular router, due to
their reliability, versatility and low cost. A Cisco 2500 series router can
easily be picked up on eBay for around $100 CND.

Figure 1: Cisco 2501 Router

Features
will vary based on model number so for this article we will focus on the Cisco
2501 router – one of the most common models out there.

When
you are talking about features on a Cisco router, you are usually referring to
the interfaces it has and the storage (RAM, NVRAM, Flash) that it has. An
interface, for the purposes of this article, can be thought of as the physical
port on the router. Let’s begin by discussing the different interfaces on the
2501.

The
first interface, to the far left in Figure 1, is labeled ‘AUI’ or Autonomous
Unit Interface. This is actually an Ethernet interface. How does it connect to
a standard Ethernet cable? It requires a piece of equipment known as a Transceiver. The only thing you really
need to know about a Transceiver is that it can be thought of as an AUI to
Ethernet adapter. This interface is known as Ethernet0 by the router.

Figure 2: A Transceiver

Next,
we have two Serial Interfaces, Serial0 and Serial1. These interfaces allow you
to connect via a synchronous serial cable to other Cisco routers within your
LAN. We won’t get into all of these details, but it is at least good to know
what the interface is for.

The
two RJ-45 connectors to the right of the serial interfaces are the Console and
AUX interfaces, respectively. The console interface is how we will connect to
the router for the first time to configure it. To do this, we need a special
console cable. One end is a standard DB9 and the other is RJ-45. It is
interesting to note that this cable is flat! This makes it easy to keep track
of the cable in amongst all of your Ethernet cables. The AUX interface will not
be discussed in this article.

Figure 3: A Console Cable

Setting Up & Configuring Your Router

Let’s
get started! First, you will need to plug your router in with a power cord.
Next, connect the console cable to the Console port on the router and also to a
serial port on your computer. That is really all you need to do to start
playing around with the router. You can go ahead and fire that router up.

On
your computer, launch Start > All Programs > Accessories > Communication
> HyperTerminal. It should be noted that Windows Server 2003 does not
include this application. You can copy the application and its DLLs from a
Windows XP or 2000 computer and it will work just fine.

In
HyperTerminal, you will be prompted with the New Connection window. You can
name the connection whatever you like and choose an icon for it. Select the
proper COM (Serial) port and continue to the next screen. You will need to set
the options like this:

Figure 4: HyperTerminal Session Options

After clicking on OK, you
will be brought to a white screen. Pressing Enter will initiate the session.
You will then have the first prompt:

Router>

This is known as User Mode.
From here, you can not perform any configure options and the commands you can
enter are limited. At any time in the Cisco IOS (Internetwork Operating
System), you can get a list of commands by typing ‘?’.

From User Mode, we can view
information about the router, such as its IOS version, the amount of memory
installed in it, the router’s Routing Table and a few more useful things. In
the User Mode, let’s try a commands to show you what type of hardware the
router has.

show version output from a 2514 router:

Production>show
version

Cisco
Internetwork Operating System Software

IOS
(tm) 2500 Software (C2500-DS40-L), Version 11.2(5)P, SHARED PLATFORM,
RELEAS

E SOFTWARE
(fc1)

Copyright
(c) 1986-1997 by cisco Systems, Inc.

Compiled
Mon 07-Apr-97 17:39 by tej

Image
text-base: 0×03037DD8, data-base: 0×00001000

ROM:
System Bootstrap, Version 11.0(10c), SOFTWARE

ROM:
3000 Bootstrap Software (IGS-BOOT-R), Version 11.0(10c), RELEASE SOFTWARE (fc1)

Production
uptime is 1 day, 2 hours, 24 minutes

System
restarted by power-on

System
image file is "flash:80135205.bin", booted via flash

cisco
2500 (68030) processor (revision L) with 2048K/2048K bytes of memory.

Processor
board ID 06033664, with hardware revision 00000000

Bridging
software.

X.25
software, Version 2.0, NET2, BFE and GOSIP compliant.

2
Ethernet/IEEE 802.3 interface(s)

2
Serial network interface(s)

32K
bytes of non-volatile configuration memory.

8192K
bytes of processor board System flash (Read ONLY)

Configuration
register is 0×2102

Next thing we’ll do is log in to Privileged Mode. To
do this, you simply type:

enable

This changes the prompt to:

Router#

From this mode, we have many more command options to
choose from. You can type ‘?’ to get a list of the available commands.

I will let you browse around for yourself in the IOS,
but I will provide you with information on doing a few of the major tasks to
get the router functional.

First of all, lets configure your Ethernet interface
with an IP Address. To do this, we must be in what is called Global
Configuration Mode. To enter this mode, type

Router#configure
terminal

or

Router#config
t

To notify you that you are in Global Configuration Mode,
your command prompt changes to:

Router(config)#

You will probably want to set a password to get into
Privileged Mode so there can be no unauthorized changes made.

Router(config)#enable secret yourpasswordhere

Next, we must specify that we want to configure the
interface Ethernet0.

Router(config)interface
Ethernet0

Or

Router(config)#int
e0

Because you are configuring an interface, the prompt
changes to:

Router(config-if)#

From here, we can issue the command that will
configure the IP Address. I have included a sample address. You would use your
address in the command. Don’t forget to put the correct subnet mask!

Router(config-if)#ip
address 192.168.10.254 255.255.255.0

By default, all interfaces on the router are shutdown

Router(config-if)#no
shutdown

or

Router(config-if)#no
sh

We want to make the router aware of the networks it
is responsible for. To do this, we must configure a Routing Protocol on the
router. We will not get into great detail about Routing Protocols, since it is
a lengthy topic. For the purposes of this article, we will be using the Routing
Information Protocol (RIP) protocol. To enable this, we must first exit the
interface.

Router(config-if)#
exit

To enable RIP, two steps are required. First me must
define which protocol we are using, and secondly we must specify which networks
the router is to concern itself with.

Router(config)#router
rip

Router(config-router)#network
192.168.10.0

Notice that the prompt changed to tell you that it
was in router configuration mode. The last thing we will configure is Telnet
access so you can work on the router from an IP address rather than through a
console cable. You must exit router configuration mode:

Router(config-router)#exit

Do to the scope of this guide, I will simply list the
commands required to allow Telnet connections. In a future article, the theory
behind this may be covered.

Router(config)#line
vty 0 4

Router(config-line)#login

Router(config-line)#password
yourpasswordhere

Now that we’ve got a working router, it is important
to save the configuration from RAM to NVRAM. To do this, we type:

Router#copy
run start

Now that you have configured your router, you can telnet
to it from any computer in your network.

Start > Run > cmd

telnet 192.168.10.254

Figure 5: A Telnet Session

Further Reading