InterVLAN Routing requires that routing be enabled for the layer 3 protocol – eg. IP Routing requires static routes or a dynamic routing protocol by default every port on most catalyst switch platforms is layer 2, and on 6500’s every port is layer 3 by default to determine the mode a switch port is in: […]
Protecting The Spanning Tree Protocol Topology There are 2 conditions that can occur to disrupt the loop free topology even when STP is running: BPDU’s suddenly being received on a port that shouldn’t be receiving them – can result in unexpected re-convergence results BPDU’s suddenly stop being received on a port that should be receiving them […]
STP Root Bridge Root bridge location should be determined as part of the design process. Adjustments to the STP configuration can be made for things like using redundant links to load balance in parrallel, or configuring STP to converge quickly and predictably if a major topology change occurs. note – if STP has […]
Overview defined in IEEE 802.1D. provides network link redundancy, so that a layer 2 switched network can recover from failures without intervention in a timely manner. solves the problem of bridging loops (forwarding a single frame around and around between two switches) enables switches to become aware of each other in order to negotiate a […]
Rapid Spanning Tree Protocol IEEE 802.1D – original STP, topology change takes 30 seconds before port goes from blocking to forwarding IEEE 802.1w – RSTP, much faster convergence, as with STP can be applied as a single instance or multiple instances by using RSTP with Cisco’s own PVST+, resulting in Rapid PVST+. Can also be […]
Switch Port Aggregation with Etherchannel 2 to 8 links of 100mb, 1gb or 10gb can be bundled as one logical link of Fast Etherchannel (FEC), Gigabit Etherchannel (GEC), or 10 Gigabit Etherchannel (10 GEC) respectively, giving a full duplex bandwidth of up to 1600mbps, 16gbps or 160gbps. There are no spanning tree issues […]
Static VLANs Port-based membership. End user devices are members of VLANs based on the physical switchport they are connected to, and are not aware of which VLAN they are in. Ports are assigned to VLANs by an administrator and the port receives a Port VLAN ID (PVID) that links it to a VLAN number. Switchports […]
Ethernet Ethernet (10Mbps) – IEEE 802.3, 10mbps bandwidth between users, shared medium, both a collison domain and and a broadcast domain, CSMA/CD = half-duplex operation, more devices sharing the medium = more collisions = poor performance. Ethernet switching allows full-duplex operation due to the fact that the switch dynamically allocates a dedicated 10Mbps to each […]
Layer 2 Switch Operation An ethernet switch decides where to forward incoming frames based on the destination MAC address contained within the received frame. Using this method means that the ethernet media is no longer shared between all connected devices. A switch will not forward a frame unless it knows which switch port the destination […]
As part of my prep for the exam, I attended the Implementing Cisco IP Switched Networks training course in Manchester this week. The course was run by QA Training and delivered by an instructor from Fast Lane. The course follows the official Cisco curriculum and for the lab exercises the students work in pairs on actual […]