Free CCNA Training Course | Part 3 - Spanning-Tree Welcome to the Free CCNA Training Course. This series is for anyone who wants to build on their basic network skills, and even pass the CCNA 200-301 exam. Part 1 of this series starts with Layer-2/Switching technology. This covers topics like general switching, VLANs, Interfaces, Spanning-Tree, RSTP, Etherchannels, and Power Over Ethernet (PoE). The website has additional links for further study to take you to the next level. Links are at the end of the description. In this video, we’re going cover: 0:00 Overview 0:30 The Need for Spanning Tree 2:47 BPDUs and the Root Bridge 8:14 Root Ports and Port Cost 11:50 Loops and Blocking 14:00 Port States and Timing 16:08 Topology Changes Switches typically operate at layer-2, and at layer-2 we can get loops. If we have a loop, a broadcast could cause a broadcast storm by flooding frames through the VLAN, which loop indefinitely. Spanning Tree (AKA, Spanning Tree Protocol or STP) identifies loops in the topology, and breaks them. Spanning-tree elects one switch as the root bridge. Special messages called BPDUs (Bridge Protocol Data Unit) help switches learn about the topology. Each switch has a Switch ID, and a bridge priority (which is always divisible by 4096). The best bridge priority determines the root bridge. BPDUs from a switch with a lower priority are inferior BPDUs, while BPDUs with better priorities are superior BPDUs. In the topology, ports facing the root bridge are the root ports. Ports facing away are said to be designated. Each port has a cost. The path to the root bridge is an accumulation of these costs, called the path cost. The shortest path cost is the root port (and there is only ever one per switch). Alternate paths to the root bridge are loops, and will be blocked. All ports go through the phases Blocking, Listening, Learning, and Forwarding, while they decide what their role in the network will be. When there are changes, a TCN BPDU (Topology Change Notification) is sent out. Study Notes (free): https://networkdirection.net/study-notes/cisco-ccna-study-notes/ccna-spanning-tree Transcripts (free): https://networkdirection.net/study-notes/cisco-ccna-transcripts/ccna-spanning-tree Quizzes (for members): https://networkdirection.net/labsandquizzes/quizzes/cisco-ccna-quizzes/ccna-spanning-tree-review Labs (for members): https://networkdirection.net/labsandquizzes/labs/cisco-ccna-labs/ccna-spanning-tree Thank you for watching out Free CCNA Training Course Patreon information: https://networkdirection.net/patreon/ LET'S CONNECT 🌏 null 🌏 https://twitter.com/NetwrkDirection 🌏 https://www.patreon.com/NetworkDirection 🌏 https://www.networkdirection.net/ #NetworkDirection #networking #CCNA #200-301