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Subnetting Mastery

Lately I’ve been working on a Subnetting Mastery video series. The goal is take someone with little to no exposure to subnetting and make them a subnetting pro. I’m happy to announce that the video series is finally complete! If anyone is working through or trying to learn subnetting, this is the video series for […]

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Cisco ASA NAT – Configuration Guide

This article provides all the information you need to understand and configure NAT on Cisco ASA and Cisco ASA-X Firewalls. There are  four possible methods of address translation, and each were defined in the Network Address Translation article series: Static NAT, Static PAT, Dynamic PAT, Dynamic NAT. This article assumes prior knowledge of each of […]

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Cisco NAT Configuration – IOS Router

In this article, we will illustrate the Cisco NAT configuration on IOS Routers. This is a follow up article to the Network Address Translation article series which thoroughly covered the operation of NAT and answers the questions “What is NAT?” and “How does NAT work?“. There are only four types of network address translation: Static NAT, Static PAT, […]

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VPN with Overlapping Networks

When connecting two sites together using a Virtual Private Network (VPN), a common issue that is encountered is trying to build a VPN with overlapping networks — where both sites happen to use the same Private IP addresses. In such cases, hosts on one side of the VPN tunnel will be unable to communicate with […]

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Cisco NAT Terminology

Cisco has created some NAT terminology which explicitly refer to the IP addresses and/or ports involved in Network Address Translation (NAT). While discussing the addresses involved in a NAT, using the terms like “Source” and “Destination” are common. However, using such terms can create some ambiguity. Specifically, the terms “Source” and “Destination” can create confusion […]

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BGP Oldest Path

BGP is the predominant dynamic routing protocol used to exchange routes between different autonomous systems. BGP’s popularity lies in the Path Selection process which allows extremely granular control of the path for incoming and outgoing traffic. One of the steps in this process states that if a tie still exists between two paths, BGP will […]

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Communication through Multiple Switches

In a previous article we demonstrated how a single switch functions. One of the most frequent requests I receive is asking how the process would be different if there were multiple switches. This article will illustrate the process using two switches. In the Packet Traveling series, we discussed the four specific functions of a switch: Learning, Flooding, Forwarding, […]

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Routing Between VLANs

We wrote an article which covers Virtual Local Area Networks (VLANs) as a concept, and another article on configuring VLANs on Cisco witches. The remaining subject to cover is the different options that exist for routing between VLANs. Why do we need Routing Between VLANs? As we learned in a prior article, VLANs create a logical separation […]