Archive for the 'Cisco Tutorials' Category

Static NAT overloaded???

Wednesday, July 27th, 2011

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 ( & The IP address on the outside interface has been configured [...]

Configuring PAT on Cisco Routers (NAT Overload)

Wednesday, July 20th, 2011

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 [...]

Configuring Dynamic NAT on Cisco Routers

Friday, July 15th, 2011

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 [...]

Configuring Static NAT on Cisco Routers

Thursday, July 7th, 2011

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 (Network Address Translation)

Monday, September 21st, 2009

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. [...]

Creating Layer 2 and Layer 3 Ether Channels

Friday, August 28th, 2009

In order to bundle multiple interfaces between switches in an effort in increase throughput, a Ether Channel can be created.   Ether Channels can be created as Layer 2 or Layer3. The obvious difference between the 2 is that a Layer 3 link will have a IP address associated and hence traffic can be routed between [...]

ISDN and Multilink with load-threshold

Thursday, August 27th, 2009

ISDN is a fantastic option as a backup in cases where your primary link has failed. However often your primary line has much more bandwidth than a single ISDN line (Channel). The ISDN BRI B-Channels run at 56kb/s or 64 kb/s (depending on country) and although this is a good start, often you need more [...]

Floating Static Routes

Wednesday, August 26th, 2009

In order to have a fully fault tolerant network, a backup solution for WAN links is vital. There are many options for configuring a backup line incase the primary line fails and in this tutorial we are going to look at using floating static routes to achieve a dial-up connection to act as our backup [...]

Configuring Basic ISDN with Interesting Traffic

Tuesday, August 25th, 2009

When configuring ISDN with interesting traffic, it’s important to first understand how Cisco defines ‘interesting’ and what this means in terms of the connection been formed. Interesting traffic is traffic that we define in the form of an access-list that is allowed to cause the ISDN to dial. This does NOT mean it is the [...]

ISDN Switch-type

Monday, August 24th, 2009

In order for any ISDN lines to establish Layer-1 connectivity the switch-type has to be defined correctly. The switch-type is very much country dependant so it’s also important to memorize the switch-type that applies to where you do most of your installations.   If Layer-1 is showing ‘Deactivated’ when using the show isdn status command, [...]