PAT - NAT overload

In this post I will talk about NAT overload also known as PAT.

NAT

In this post I will explain how NAT works. For this article I used the network-diagram below. The network represented is just a very basic network, I used RIPv2 in this example.

IP split-horizon

When this rule is enabled it will not send updates out the interface it received it on. When this rule is disabled it will send updates out the interface it was received on.

BGP Attributes - Weight

In the previous posts I explained how AS-prepend, MED and Local Preference works. In this post I will explain how weight works.

BGP Attributes - AS Prepend

In the previous posts I explained how MED and Local Preference works. In this post I will explain how as prepend works.

BGP Attributes - Local Preference

In the previous post I explained how MED (Multi-Exit Discriminator) works. In this post I will explain how Local Preference works.

BGP Attributes - MED (Multi-Exit Discriminator)

In this article I will show how MED (Multi-Exit Discriminator) works. For this article I used the topology from the previous MPLS posts.

BGP Path Selection

Below is the BGP path selection process which I copied from Cisco’s site :

MPLS - Basic MPLS Part 2

In this part I will show the configurations to make this MPLS network work. Below the picture you can see the relevant configurations.

MPLS - Basic MPLS Part 1

Recently I decided to start looking into CCIE SP. Since I already am a CCIE R&S CCIE SP seems to be the logical next step. Below you can see a topology I created with GNS3. It is a simple MPLS network just to start things off for me.

Complex access-lists

“there are 10 kind of people, those who understand binary and those who don’t….”

In this post I will try to explain how to compute complex access-lists. Say we had the following ip-addresses and we needed to make an access-list for it with as little rules as possible that would only match the ip-addresses specified.

OSPF / Frame Relay Part 1

In this tutorial I will try to explain the different ways to set up frame-relay topologies in conjunction with OSPF. The topology I will use for this is the same one as I used before in the NTP and URPF posts.

For the most basic topology where R1 is the HUB and R2 en R3 are [...]

NTP example

NTP synchronizes timekeeping among a set of distributed time servers and clients. This synchronization allows events to be correlated when system logs are created and other time-specific events occur.

See below an example of an NTP configuration

Time-based ACL

Time based ACL Example :

Ever needed to create a time-based ACL?

The following example denies HTTP traffic on Monday through Friday between the hours of 8:00 am and 6:00 pm:

URPF tutorial

The Unicast RPF feature helps mitigate problems caused by the introduction of malformed or forged (spoofed) IP source addresses into a network by discarding IP packets that lack a verifiable IP source address
So in other words, when you enable ip verify unicast on an interface what it basically does is check if the source address [...]