Description

Switched Ethernet has been the dominant LAN technology for more than a decade and VLAN-based switched infrastructures are at the core of every campus network. A good understanding of the processes involved in Layer 2 switching and being able to diagnose and resolve Layer 2 switching problems in those environments is a fundamental skill that any network engineer should have. A primary tool in building highly available networks is the use of redundant devices and links. With these redundant links, bridging loops can be introduced, resulting in broadcast storms that can potentially cripple the network. The Spanning Tree Protocol (STP) acts as a safety net by breaking those loops and preventing broadcast storms. Spanning tree failures can be catastrophic when they happen, so recognizing the symptoms and having an action plan for these types of failures is a skill that is essential in reducing network downtime. The traditional distinction between routers and switches has become blurred over the past decade and multilayer switches have taken over the role of the router in the campus LAN environment. It is important for network engineers to understand the differences between hardware-accelerated Layer 3 switching and software-based routing architectures, and how these differences translate to the troubleshooting process. In this course, the Layer 2 switching process and associated switch data structures are reviewed, as is the diagnosing of VLAN and trunking problems using the Cisco IOS command line interface. It will also explain how to diagnose spanning-tree problems using the Cisco IOS command line interface. Multilayer switching concepts and how to diagnose specific problems related to multilayer switching, switched virtual interfaces (SVIs), and inter-VLAN routing are also detailed.