By default VLAN 1 is the native VLAN for an interface configured in switchport mode Trunk/General. If you want VLAN 1 to be tagged, you will need to change the native VLAN to something other than 1 and then tag VLAN 1.  Example: Console(config)# interface ethernet 1/e16 Console(config-if)# switchport mode trunk Console(config-if)# switchport trunk native vlan 99 Console(config-if)# switchport trunk allowed vlan add 1  You could also use General mode. Example: Console(config)# interface ethernet 1/e16 Console(config-if)# switchport mode general Console(config-if)# switchport general pvid 99 Console(config-if)# switchport general allowed vlan add 1 tagged 
Hello all ...  Please need help !! I want to configure the VLAN 1 on dell 3524 because the VLAN 1 has DHCP IP from the Mikrotik, how to configure the default VLAN 1 to trunk mode ?thanks :)
Trunk Vlan 1 on Dell 3524 switch