Switchport Mode Trunk Allow-Null - Planet SGS-6341 Series Command Manual

Default:
The port is in Access mode by default.
Usage Guide:
Ports in trunk mode is called Trunk ports. Trunk ports can allow traffic of multiple VLANs to pass
through. VLAN in different switches can be interconnected with the Trunk ports. Ports under access
mode are called Access ports. An access port can be assigned to one and only one VLAN at a time.
Hybrid ports can allow traffic of multiple VLANs to pass through, receive and send the packets of
multiple VLANs, used to connect switch, or user's computer. When Hybrid ports and Trunk ports
receive the data, the deal way is same, but the deal way is different in sending the data. Because
Hybrid ports can allow the packets of multiple VLANs to send with no tag, however, Trunk ports can
only allow the packets of the default VLAN to send with no tag. The attribute of ports can not directly
convert between Hybrid and Trunk, it must configure to be access at first, then configure to be
Hybrid or Trunk. When the Trunk or Hybrid attribute is cancelled, the port attribute restores the
default (access) attribute and belongs to vlan1.
Example:
Set port 5 to trunk mode and port 8 to access mode, port 10 to hybrid mode.
Switch(config)#interface ethernet 1/0/5
Switch(Config-If-Ethernet1/0/5)#switchport mode trunk
Switch(Config-If-Ethernet1/0/5)#exit
Switch(config)#interface ethernet 1/0/8
Switch(Config-If-Ethernet1/0/8)#switchport mode access
Switch(Config-If-Ethernet1/0/8)#exit
Switch(config)#interface ethernet 1/0/10
Switch(Config-If-Ethernet1/0/10)#switchport mode hybrid
Switch(Config-If-Ethernet1/0/10)#exit

12.1.31 switchport mode trunk allow-null

Command:
switchport mode trunk allow-null
Function:
Add a port as trunk mode. When enabling GVRP, the mode that adds the ports with trunk mode to
all VLANs is not appropriate. Therefore, add a port as trunk port and does not join any VLANs by
default for enabling GVRP on trunk port is appropriate. It is recommended to configure a port as
trunk with this command before enabling GVRP. This command can also be used when a port has
been configured as trunk already, which equals to clearing allow-list and quits all VLANs.
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