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ccna exam israel.1 Configure the switch SLS1 (config)#spanning-tree mode pvst. 228 . Cisco Networking Lab CCNA Lab Guide (Release 2)Chia Configuring STP Mode as PVST+,Cisco Switch STP (PVST+) feature is enabled by default. you can use the command showspanning-treeS1 (config)#spanning-tree vlan 1 priority 4096S1 (config)#spanning-tree vlan 2 priority 8192 Configure the STP bridge priority for VLAN1 Configure the STP bridge priority for VLAN2S1 (config)#spanning-tree vlan 1 root primary diameter 7 Configure the switch diameter, the default value of Cisco switch is 7, and the adjustable range is 2.7eat [end-of-technology extension].The command spanning-tree vlan vlan-id root primary can also control the root bridge election of STP, it is actually macro command, when executing this command the switch will first take out the current priority of the root bridge, and then usually the priority of the root switch is subtracted from 2x4096 as the new priority of this switch STP. This command is a one-time command. you do not see this command in the configuration file using the show running-config command. instead, you see the modified STP priority. and this command does not guarantee that the switch will always be the root bridge. if another switch configures a lower priority value with the command spanning-tree vlan vlan-id priority priority to configure a lower priority value, the switch loses its root bridge position. The spanningtree vlan vlan-id root primary command is usually used in conjunction with the spanning-tree vlan vlan-id root secondary command, and the switch executing the spanning-tree vlan vlan-id root secondary command first The switch will first fetch the priority of the current root bridge, under the premise of ensuring that this switch becomes the secondary root bridge of STP, and then usually subtract the corresponding value from the priority of the root switch STP as the new priority of this switch STP. Both of the above two commands have limitations, one is that the administrator cannot explicitly control the size of the priority; second, sometimes the effect of controlling the root bridge election may not be achieved, for example, if the switch with priority 0 is already the root bridge, it may not be appropriate to execute the above command again. Therefore, it is recommended that the administrator specify the root bridge priority manually. The spanning-tree vlan vlan-id root primary command is more often used to modify the switch network diameter by the diameter parameter after it, that is, after using the spanning-tree vlan vlan-id root primary diameter number command to modify the value. The maximum aging time and forwarding delay of STP's timer change. it is recommended that you do not modify it unless the administrator is absolutely sure. the value defaults to 7.SI (config)#interface range fastEthernet 0/1-4 S1(config-if-range)#spanning-treeportfast Configuring Edge Ports %Waming: portfastshouldonlybeenabledonports connectedtoasinglehost. connectinghubs,concentrators,switches,bridges,etc... UsewithCAUTION o%Portfastwillbeconfiguredin20 interfaces due to the The above alarm message indicates that these interfaces are in anon-trunking mode.The above warning message suggests that these ports should only be used to access computers, not other devices such as hubs, concentrators, switches and bridges, and that the edge ports may cause temporary loops when they are activated. It also suggests that this command is only valid for non-Trunk ports. If an edge port is configured on a Trunk port, the corresponding command is spanning-tree portfast trunk, for example, the port is connected to a router interface that uses single-arm routing for inter-VLAN communication. When a computer is connected to a switch configured with an edge port, the port immediately enters the forwarding state without waiting for spanning tree convergence. However, if a BPDU is received on a port configured as an edge port, it immediately loses its edge port characteristics and participates in normal STP operations