So we have already looked at all 3 possible NAT configurations, however there is one more trick that is always useful to know. How to overload a Static NAT. Let’s assume the following for this example We have 2 public IP addresses (192.168.1.1 & 192.168.1.2) The IP address on the outside interface has been configured [...]

PAT (Port Address Translation) is by far the most common implementation of NAT, and if you have an ADSL router at home there is a 100% chance you are using it. PAT or otherwise known as NAT overload, allows you to translate IP addresses in a many-to-one method. In my previous post on Configuring Dynamic [...]

In my last post Configuring Static NAT on Cisco Routers we saw how you can translate 1 IP address into another single IP address. This tutorial will cover how to translate many IP addresses into many IP addresses, otherwise referred to as many-to-many translation. Dynamic NAT allows us to translate many IP addresses into a [...]

In my previous post on NAT, I explained the difference between the 3 different types of NAT that can be configured. In this tutorial I’m going to cover the configuration steps to configure static NAT. Static NAT is a one-to-one mapping. It allows us to translate a single IP address into a different single IP [...]

NAT or Network Address Translation is a key function required in every organisations network. Since all organisation use RFC 1918 IP addressing, and these IP addresses are not allowed to exist on the internet, before we send packets to the internet we need to translate the internal IP address into a useable public IP address. [...]

One of the first and most important things to configure on any Cisco device after allowing telnet or SSH, is to restrict who is allowed to access the device. Of course having a password on the lines is the first step but if telnet is the method of communication, all passwords will be sent over [...]

Before looking into the configuration of ACL (Access Control Lists), it’s important to get some of the concepts and understanding of how they work and what they are used for. Firstly, most people believe that ACL’s are used purely for denying or allowing traffic, although this is certainly one of the functions of a ACL [...]

In order for 2 VLANS to be able to communicate, the traffic must be routed. This can be done either by a multi-layer switch which will have routing capabilities, or the packets can be routed by a router.   As an example, I have 2 VLANS, VLAN 10 and VLAN 20 which have subnets 10.0.10.0/24 [...]

VTP (VLAN Trunking protocol) is a protocol used to replicate the VLAN information across switches, however there are a few things that must be made clear…   1/ VLAN information will only be sent on trunk ports 2/ Only the VLAN identity is replicated, NOT which ports are configured to use that VLAN! 3/ Maintains [...]

A VLAN is a Virtual LAN which allows us to logically separate computers on our network.   In previous years, an office would have a physical switch or hub in each office, and offices were structured around the job function. In other words, all sales people would be in the same office and would all [...]