Before we can discuss how NAT works, we must discuss the purpose of NAT and answer the question, “Why NAT?” In the original plan for the Internet, every host was meant to have its own unique IP address. This means if you had a network which had 30 hosts, you would need 30 unique IP […]
ARP in 5 Minutes
September 14, 2017 By Leave a Comment
Here is a quick video that teaches the basics of Address Resolution Protocol (ARP) in less than 5 minutes. If you want to go deeper on ARP and all of its variants, check out the Address Resolution Protocol article series.
BGP Oldest Path
May 10, 2017 By 5 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, […]
Address Resolution Protocol (ARP)
February 5, 2017 By 3 Comments
An IP address is the logical addressing scheme for nodes on a network. IP Addresses exist at the Network layer of the OSI Model and help facilitate the L3 goal of “end to end” delivery. A MAC address is the physical addressing scheme for individual NIC cards on each node of a network. MAC addresses […]
ARP Probe and ARP Announcement
January 30, 2017 By 7 Comments
We finally come to the last iteration of ARP that this article series will discuss. They are the ARP Probe and the ARP Announcement. Both of these are used in a process known as Duplicate Address Detection. The idea is if a host acquires and puts to use an IP address that happens to already […]
Gratuitous ARP
January 23, 2017 By 31 Comments
We’ve talked about Traditional ARP, where a node is requesting another node’s MAC address. We’ve also talked about Proxy ARP, where a node is answering an ARP request on behalf of another node. Which brings us to another iteration of ARP known as Gratuitous ARP. A Gratuitous ARP is an ARP Response that was not prompted […]
Proxy ARP
January 16, 2017 By 14 Comments
We’ve discussed the use cases and role of traditional ARP in the prior article of this series. In this article we will discuss Proxy ARP and its role and significance. Proxy ARP occurs when one node is responding to an ARP request on behalf of another node. Proxy ARP is not a malicious event, it […]