9 Steps to Setting Up a Cisco Router

Working with a Cisco router and the Cisco Internetworking Operating System (IOS) is a great way to experiment with networking concepts and gear and could be good for your career development. You can get some hands-on IOS experience by setting up a Cisco router at the Internet edge in your test lab at work or in your home office. A Cisco router allows you greater flexibility (with more granular controls than the Linksys or NETGEAR hardware commonly used in home offices) if you later want to expand your setup to include, say, a Microsoft ISA Server firewall on the back end.

Let’s go through the basic steps of setting up a Cisco router to provide Internet access to a small network. I’ll assume you have some basic IOS knowledge, including how to log on and how to save and clear configurations. I’ll also assume that you have a solid understanding of networking, including what Network Address Translation (NAT) is. I won’t cover items such as setting up Secure Shell (SSH) access and hardening access lists. You can expand into those areas as you feel comfortable and want to experiment more.

What You’ll Need
You need a Cisco router with at least two Ethernet interfaces. An 806, 836, 851, or 871 is ideal for a home or small office setup—in fact, that’s what those models are geared towards. You can buy an 851 for a few hundred dollars from various online retailers. However, a 2610 works just as well, and you might have one sitting in the equipment bin at your office that you can ask to borrow.

Your router should have IOS 12.2 or later. This article is based on a Cisco 851W with IOS 12.4, including the IOS firewall feature set.

You also need a Cisco console cable (sometimes called a rollover cable). One end has an eight-position, eight-conductor modular jack to connect to the router; the other end has a DB-9 serial connector. In recent years, the console cables that Cisco has shipped with its equipment have been light blue.

You need a computer with a DB-9 serial port. In my experience, USB-to-serial converters work just fine for this application. You also need a computer with a terminal emulation program. Hilgraeve’s HyperTerminal is available with Windows XP, but it was removed from Windows Vista. Vista users can download Hyper- Terminal Private Edition 6.3 at www.hilgraeve.com/htpe/download.html. Mac OS X users can Google for ZTerm, and Linux users, for minicom.

1. Connect the router to the PC, and start a terminal emulation program
Connect your router to your PC with the console cable, and fire up your terminal emulation program. The port settings are 9600,8,N,1. If you’ve never before accessed a device directly via an asynchronous serial connection, you might want to ask a Cisco veteran for some assistance.

Start with the command enable to get into privileged EXEC mode. Then type the command erase startup-config to get a blank configuration. Next, restart the router with the reload command. Make sure to say no to an IOS prompt that asks if you’d like to enter the initial configuration dialog.

These steps might sound confusing if you’ve worked only with Cisco devices that are up and running in production. In that case, you’re probably more accustomed to using Telnet, or preferably SSH, to configure the equipment. That isn’t an option when you want to start with a blank configuration, which will prevent any Telnet or SSH access to the equipment for the time being.

2. Identify the router’s interfaces
Take a look at the back of your router and identify which Ethernet ports you’ll be using for what. One will connect to your WAN device, such as a cable modem; another will connect to your LAN. If you’re using an 851W, like me, you’ll notice that the ports are labeled for you—FastEthernet4 is the WAN interface and FastEthernet0 through FastEthernet3 are the LAN interfaces. The 851 includes a built-in four-port switch, hence the four LAN interfaces.

If your router’s interfaces aren’t labeled, you can type the command

 show ip interface brief

from privileged EXEC mode to find the names.

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