The Native VLAN is an oft confused concept, though it needn’t be. This video will explain what the Native VLAN is and how it affects traffic on a wire. Summary An Access port (or “untagged port” in the non Cisco world) is a switch port which carries traffic for only one VLAN. A Trunk port […]
Subnetting Mastery
August 3, 2018 By 2 Comments
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 […]
Cisco ASA NAT – Configuration Guide
April 16, 2018 By 69 Comments
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 […]
Cisco NAT Configuration – IOS Router
January 18, 2018 By 10 Comments
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, […]
VPN with Overlapping Networks
December 5, 2017 By 10 Comments
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 […]
Cisco NAT Terminology
November 15, 2017 By 4 Comments
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 […]
BGP Oldest Path
May 10, 2017 By 6 Comments
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 […]
Communication through Multiple Switches
February 9, 2017 By 27 Comments
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, […]