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Catalyst4500 Series SwitchCiscoIOS Command Reference—Release 12.2(18)EW
78-16201-01
Chapter2Cisco IOS Commands for the Catalyst 4500 Series Switches
switchport trunk
switchport trunk
To set trunk characteristics when an interface is in trunking mode, use the switchport trunk command.
To reset all of the trunking characteristics back to the original defaults, use the no form of this command.
switchport trunk encapsulation {isl | dot1q | negotiate}
no switchport trunk encapsulation
switchport trunk native vlan {tag | vlan_id}
no switchport trunk native vlan {tag | vlan_id}
switchport trunk allowed vlan vlan_list
no switchport trunk allowed vlan vlan_list
switchport trunk pruning vlan vlan_list
no switchport trunk pruning vlan vlan_list
Syntax Description
Defaults The default settings are as follows:
• Encapsulation type is dependent on the platform or interface hardware.
• Access VLANs and trunk interface native VLANs are a default VLAN corresponding to the platform
or interface hardware.
• All VLAN lists include all VLANs.
• Native VLAN tagging is enabled on the port if enabled globally.
Command Modes Interface configuration
encapsulation isl Sets the trunk encapsulation format to ISL.
encapsulation dot1q Sets the trunk encapsulation format to 802.1Q.
encapsulation negotiate Specifies that if DISL and DTP negotiation do not resolve the
encapsulation format, ISL will be the selected format.
native vlan tag Specifies the tagging of native VLAN traffic on 802.1Q trunks.
native vlan vlan_id Sets the native VLAN for the trunk in 802.1Q trunking mode.
allowed vlan vlan_list Sets the list of allowed VLANs that transmit this interface in tagged
format when in trunking mode. See “Usage Guidelines” for formatting
guidelines for vlan_list.
pruning vlan vlan_list Sets the list of VLANs that are enabled for VTP pruning when the switch
is in trunking mode. See “Usage Guidelines” for formatting guidelines
for vlan_list.
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