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 […]
SubSeven – aka: Sub7 and Sub7Server is a backdoor program, in the form of a Trojan, used mostly for causing trouble on computer networks. It can be used for simple attacks such as hiding the mouse cursor and opening applications, but it can also be used for more serious attacks including retrieving all your personal […]
The big difference between the enable password and the enable secret is the encryption level. The enable password by default is saved in clear text so when looking at the running-configuration of the router you will be able to read the password. It is possible to encrypt this password using the service password-encryption command. The […]
Before looking at how to mitigate a Smurf attack, let’s first understand what it is and why it’s such a problem. A Smurf works on a weakness of IP and ICMP by sending an ICMP packet to the broadcast address of a network. For example, I could send an ICMP (Ping packet) to every computer […]
IP spoofing is the act of camouflaging your IP address to make it look like you are someone else. Although IP spoofing is not an attack by itself, it is the starting point of many of the most common attacks found on today’s networks. Most, but not all, of the spoofing attacks that take place […]
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 and often configured correctly. The unfortunate thing about password security, especially when discussing telnet, […]
In order to control what machines are plugged into your network, Cisco introduced the “switchport port-security” command. In this tutorial I’m going to explain how to use this command, and different options available using it. Below is the breakdown of the commands I used in the live demo, and an explanation of each. AOIP.ORG_Switch# terminal […]
As part of any management and audit solution for networking, Syslog is vital. Syslog messages allow us to track system error messages, exceptions, and other information, such as device configuration changes. It allows for historical reporting, depending on the application keeping the logs, as well as help in fault finding. Cisco devices support 8 levels […]
Secure Shell (SSH) is a protocol that allows us to connect to devices securely by using encryption. Gone are the days were most networking engineers are happy with using plain telnet with it’s clear text transmission of data which could result in an attacker sniffing the line for usernames and passwords. Configuring SSH on a […]