Creating Trunks
In this guide we will cover how to create a static trunk between switches and filter the VLANs across the link.
We must create a static trunk on Ethernet0/3 between SW1 and SW2.
To create a trunk, we must go into the sub-configuration mode of ETH 0/3
SW1#conf t # This command puts us in Global Config mode
SW1(config)#interface ethernet 0/3 # This command puts us into the interface sub-configuration mode
SW1(config-if)#switchport trunk encapsulation dot1q # This command will set the trunk to use the IEEE 802.1q Encapsulation standard
SW1(config-if)#switchport mode trunk # This command will statically set the interface to trunking mode.
The complete configuration for both switches is shown below
Creating a static trunk on our SW1 Creating a static trunk on our SW1 Filtering VLANs on trunk ports
To filter the VLANs and add or remove the VLANs allowed across a trunk, we use the commands below.
SW1(config-if)#switchport trunk allowed vlan 1,10,20,30 # This command will only VLANs 1,10,20,30 across the trunk
SW1(config-if)#switchport trunk allows [add | remove] vlan 40 # This command allows you to add or remove VLANs from the trunk port.
The complete configuration is shown below
Filtering the VLANs allowed across a trunk The following commands will show and verify the trunks, how they formed and what VLANs are allowed across the trunks.
SW1#show interface trunk # This command will show us the active trunks on our switch.
Show interface trunk command on SW1 
