In the previous three parts, we learned about all the interesting things that go on in the PHY with scrambling, descrambling, synchronization, auto negotiation, FEC encoding, and so on. This is all essential knowledge that we need to have to
1000BASE-T Part 3 – Autonegotiation
In this post, we’ll take a closer look at auto negotiation. Auto negotiation has the following characteristics: The Auto Negotiation transmitter and receiver is actually a separate system in its own right. In multi-speed PHY devices, auto negotiation is used
1000BASE-T Part 2 – Deepdive
In 1000BASE-T Part 1, we reviewed the layers and what their purpose is. Now we’re going to go much deeper into the layers that relate to the PHY, which is PCS, PMA, and Autonegotiation. First though, let’s review the objectives
1000BASE-T Part 1 – Introduction
How does Ethernet detect that a link goes down? This, what I thought was a simple question, I asked myself a couple of weeks ago. I realized I didn’t have a very good answer. I realized I had more to
Ethernet, STP, Topology change and the behaviour of Ethernet
Introduction This post is inspired by a post at IEOC about Uplinkfast and TCN which can be found here. Before we get to those parts, let’s recap how Ethernet and STP work together. Spanning Tree The Spanning Tree Algorithm builds
Cisco Flex link
Introduction Flex link is a Cisco solution which replaces STP in certain network topologies. It works by detecting link down on a primary interface and then bringing up the backup interface that has been defined as backup. It is most
Resilient Ethernet Protocol (REP)
Introduction I’m writing a short summary of REP as part of my CCDE studies. REP is an alternative protocol used in place of STP and is most often run in ring based topologies. It is not limited to these topologies
Detecting Network Failure
Introduction In todays networks, reliability is critical. Reliability needs to be high and convergence needs to be fast. There are several ways of detecting network failure but not all of them scale. This post takes a look at different methods
The history of Ethernet – DIX vs 802.3
I’m planning to do a post on BPDUs sent by Cisco switches and analyze why they are sent. To fully understand the coming post first we need to understand the different versions of Ethernet. There is more than one version?
Ethernet – notes
RJ 45 pinouts 10-BASE-T and 100BASE-TX uses pairs two and three, gigabit Ethernet uses all four pairs. Pinout for straight cable: 1-1;2-2;3-3;6-6 Pinout for crossover cable: 1-3;2-6;3-1;6-2 A standard PC transmits on pair one and two and receives on three