ccna exam edmonton

ccna exam edmonton.2 Forwarding delay Time that the switch is in the listening and learning stateUnderstanding the meaning of each field of BPDU is crucial to master the working principle of STP, here we focus on the Bridge ID, Path Overhead, Port ID and BPDU Timer fields.1. Bridge IDBridge ID (BridgeID,BID): used to determine the root bridge in the network, including the bridge priority, extended system ID and MAC address. The bridge ID is used in the root bridge election, and the switch with the lowest bridge ID becomes the root bridge.1 Bridge priority: A customizable value that affects the root bridge election. The lower the priority of the switch, the more likely it is to become the root bridge. The default priority value for Cisco switch STP is 32768o2 Extended System ID: Early STP was used in networks that did not use VLANs, and BPDU frames did not contain extended system IDs, and all switches formed a simple spanning tree. With the advent of VLAN technology, Cisco improved STP by adding support for VLANs, i.e., dividing the lower 12 bits in the priority field as the extended system ID, whose value is the VLAN ID, which is Cisco's version of STP, called PVST+ (Per VLAN STP, per VLAN spanning tree). The benefit of PVST+ is the flexibility to control which interfaces are to forward data or be blocked on a per VLAN basis, thus enabling load balancing. With Extended System ID, the 16 bits used to represent the bridge priority are reduced to the high 4 bits, so the bridge priority can only have a value that is a multiple of 4096 (212) in the range of 0.61440, which is a priority step of 4096. On Cisco switches, the bridge priority is added to the VLAN ID.MAC address: The base MAC address of the switch, which can be viewed with the show version command.2. Path OverheadAfter the root bridge is elected, the spanning tree algorithm determines the best path for other switches to reach the root bridge. The path overhead is the sum of all port overheads (Cost) on the path to the root bridge. oSTP uses port overhead values defined by IEEE.2 for 10 Gigabit Ethernet ports, 4 for Gigabit Ethernet ports, 19 for 100 Gigabit Ethernet ports, and 100 for 10 Gigabit Ethernet ports..218.Cisco Networking Lab CCNA Lab Guide (Release 2)