Cisco Configs Home

It can at times be like trying to find a needle in a haystack on the Cisco website when searching to find a simple config. Here you will find help for the 'less corporate' users of Cisco equipment, mainly aimed at the average Joe Bloggs home user. The following tutorials are ment to be simple and imformative. Please Choose a link from above or the following:

Home Networking

Cable Modem

I have a cable modem connection to the internet in my house, and wanted to share the connection to all the computers in the home. My cable provider NTL will only assign one IP address to one computer, I therefore needed to use NAT to forward all traffic from my cable modem to my house network. I am running a Cisco 2611 Router, and have used NAT to allow all of my home network to get on the internet.

Dialup Modem to ISP

This tutorial attempts to describe, one of the simpler method of connecting an analog modem to the AUX port on any Cisco router and configuring a Async interface which will utilize the modem to dial any standard ISP like Wannado, BT Openworld or AOL with a dialup account.

Port Forwarding for Playstation 2 Network Games

Playstation Networking Help - This config is to help game players using a Playstation 2 who wish to use the Network Adapter for networked games, particularly in NAT (Network Address Translation) setups, like the Cable Modem Setup. The basic ports that you will need to open in order to play PlayStation 2 network games are: TCP 53, 80, 443.

Port Forwarding for XBox Network Games

The first part of this tutorial will help XBox gamers configure their Cisco router to allow XBox Live traffic. The second part of this tutorial will go on to explain how XBConnect works and also how to configure a Cisco router in order for XBConnect to work.


Installing Flash Memory

A Simple Step by Step guide showing how to locate and replace the flash in a Cisco router, the installation steps to re-installing the IOS and checking everything is working. This is useful when upgrading flash memory sizes.

Catalyst 2924XL DRAM Differences

When Cisco originally released the Catalyst 2924 switch it was manufactured with only 4MB of DRAM and no support for VLAN trunking. Due to customer demand Cisco soon released the same switch with 8MB of DRAM to support the larger IOS version 12 images, and also added hardware support on switch ports for VLAN trunking.

Blocking Attacks and Viruses

Block Code Red Attacks

The "Code Red" worm is self-replicating malicious code that exploits a known vulnerability in Microsoft IIS servers (CA-2001-13). The config here shows how you can mark inbound "Code Red" hacks with the class-based marking feature, and then use ACL on the outbound interface to drop marked "Code Red" packets. This same method can be used to block other worms such as the Sadmind worm.

Block SYN Attacks

Since hearing about several recent DoS (Denial of Service) attacks on various internet servers, the method which is being used is known as SYN attacks. These attacks involve a attacker who transmits a volume of connections that cannot be completed. This causes the connection queues to fill up, thereby denying service to legitimate TCP users to services.

Block MyDoom

For all those looking for a way in which to block the W32/MyDoom (and Cousins) virus which is spreading fast across the internet, as far as I know there is not really any way in which you can use a Cisco router to block the actual virus transported within emails, in the same way in that there was no easy way to block the W32/Swen virus a few months ago. But you can block some of its actions...

Configuring a Cisco Access List to Filter IP

Everyone should have some basic filters in place on their external routers. The Cisco access control list (ACL) is probably the most commonly used object in the IOS. It is not only used for packet filtering (a type of firewall) but also for selecting types of traffic to be analyzed, forwarded, or influenced in some way.

General Configurations

AUX Port Communication

Config to allow you to use the AUX0 port to communicate through a serial (rollover) cable with a dialup modem, this can then be mapped to a specific port on the router so you can then telnet the router on that port and it will forward it directly to the modem, allowing you to issue AT commands.

Birdstep Mobile IP

The Birdstep Intelligent Mobile IP Client has followed an open, standards-based approach to provide seamless roaming for operators and enterprises. Require both wired and wireless networks. These must be logically different networks from the routers perspective.

Linux FreeS/WAN to Cisco

Linux FreeSWAN is an implementation of IPSEC & IKE for Linux. The result is Virtual Private Network or VPN. This is a network which is effectively private even though it includes machines at several different sites connected by the insecure Internet. This config shows you how you can connect a Linux FreeSWAN box to a Cisco Router to create a secure tunnel.

Switch VLAN

VLANs (Virtual Local Area Networks) are a way to structure a network logically, put simply a VLAN is a collection of nodes which are grouped together in a single broadcast domain (address range) that is based on something other than physical location.

Configuring DHCP Server

The Dynamic Host Configuration Protocol (DHCP) is an Internet protocol for automating the configuration of computers that use TCP/IP. DHCP can be used to automatically assign IP addresses, to deliver TCP/IP stack configuration parameters such as the subnet mask and default router, and to provide other configuration information such as the addresses for printer, time and news servers.

Configuring Appletalk

AppleTalk is a protocol suite developed by Apple Computer in the early 1980s, was developed in conjunction with the Macintosh computer. AppleTalk's purpose was to allow multiple users to share resources, such as files and printers. The devices that supply these resources are called servers, while the devices that make use of these resources (such as a user's Macintosh computer) are referred to as clients. Hence, AppleTalk is one of the early implementations of a distributed client/server networking system.

WAN Connections

Serial WAN Link

For the Cisco CCNA (Cisco Certified Network Associate) exam you are expected to know about WAN (Wide Area Network) links, the protocols used and how to configure a serial WAN link on a router. This tutorial will discuss these topics and end with a simple WAN lab which can be setup with mininal equipment and cost.

Compressing a T1

I recently set up a client with a T-1 to connect their 2 offices. These offices were separated by 4 cities and distanced approximately 25 miles. The only data conection they could afford is a T-1 which naturally is not alot of bandwidth. Lucky for us, Cisco provides compression (only available for serial links, such as T-1, fractional T-1, and frame).

Load Balancing across 2 T1 links

This document is for those facing the common problem of using Cisco routers to load balance IP traffic across 2 or more parallel T1's. Although the problem is common, acquiring the knowledge to address the issue can be frustratingly difficult. Hopefully this will help.

Beginners Guides

Beginner Guide to Cisco Router Configuration

This tutorial is aimed at a Cisco beginner, the document covers basic IOS operation modes, configuration and debug commands, routing operation and troubleshooting.

Beginners Guide to Access Control Lists (ACL)

The Cisco access control list (ACL) is probably the most commonly used object in the IOS. It is not only used for packet filtering (a type of firewall) but also for selecting types of traffic to be analyzed, forwarded, or influenced in some way.


ADSL Troubleshooting

ADSL Troubleshooting.

ISDN Troubleshooting

ISDN Troubleshooting.

NTL Cable Troubleshooting

NTL Cable Troubleshooting.
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