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Command Switchport Trunk Allowed Vlan Use Restricts the VLANs that can travel between a trunk on the switch. Syntax Switch(config-if)#switchport trunk allowed vlan <vlan #> Example In this example, allowed VLAN is set for int fa0/19 on SW3. CopySW3(config)#int fa0/19 SW3(config-if)#switchport trunk allowed vlan 2 Here’s the trunk …
Command Switchport Trunk Encapsulation isl Use Enables ISL trunking encapsulation on the interface. Syntax Switch(config-if)#switchport trunk encapsulation isl Example In this example, isl trunk encapsulation is enabled SW3’s fa0/2. CopySW3(config)#int fa0/2 SW3(config-if)#switchport trunk encapsulation isl Next, the trunk information is displayed for SW3. CopySW3(config-if)#do show interface trunkPort Mode …
Command Switchport Nonegotiate Use Prevents the interface from auto-negotiating trunk status. Syntax Switch(config-if)#switchport nonegotiate Example This example shows how to set fa0/19 to nonegotiate on SW3. CopySW3#conf t SW3(config)#int fa0/19 SW3(config-if)#switchport nonegotiate
Command Spanning-Tree Guard Root Use This command will disable any port that a superior BPDU is received on. This is done to ensure a switch will remain root at all times. Syntax Switch(config-if)#spanning-tree guard root Example In the below example we will configure SW1’s trunk ports to use …
Command Switchport Port-Security Maximum Use Sets the maximum number of mac addresses before a violation is triggered. Syntax Switch(config-if)#switchport port-security maximum <1-6272> Example In this example, the maximum mac addresses for int fa0/2 is set to 2 for SW3. CopySW3#conf t SW3(config-if)#int fa0/2 SW3(config-if)#switchport port-security maximum 2 Next, 2 …
Command Switchport Port-Security Use Enables port security on an interface and sets default actions. The defaults are: max mac address is 1 and the violate action is shutdown the port. Syntax Switch(config-if)#switchport port-security Example In this example, port security is configured for int fa0/2 on SW3. Note that, …
Command Spanning-Tree Port-Priority Use Sets the switches preference for the alternate paths to use if a loop is detected. Syntax Switch(config)#spanning-tree port-priority <number> Example In the below example we will configure SW2 to prefer to use Fa0/24 if a loop is detected in the network. CopySW2(config)#do show spanning vlan …
Command Switchport Trunk Encapsulation dot1q Use Enables dot1q trunking encapsulation on the interface. Syntax Switch(config-if)#switchport trunk encapsulation dot1q Example First, here is the trunking information for SW3. Note fa0/19, which is set to ISL. CopySW3(config-if)#do show int trunkPort Mode Encapsulation Status Native vlan Fa0/19 auto isl trunking 1 …
Command Switchport Mode Trunk Use Enables trunking on an interface. Before enabling trunking, encapsulation needs to be set using the switchport trunk encapsulation command. Syntax Switch(config-if)#switchport mode trunk Example In this example, trunking is enabled on fa0/2. Before enabling trunking, encapsulation is also set. CopySW3#conf t Enter configuration commands, one …
Command Spanning-Tree Portfast Use This command essentially disables spanning-tree on an interface and brings it immediately into the forwarding state. Only use this command on access ports Syntax Switch(config-if)#spanning-tree portfast Example In the below example we will configure SW1’s Fa0/2 to use port-fast to immediately skip to the …
