Chapter 9
Configuring VLANs
Interaction with Other Features
Trunking interacts with other features in these ways:
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Configuring a Trunk Port
Beginning in privileged EXEC mode, follow these steps to configure a port as a trunk port:
Command
Step 1
configure terminal
Step 2
interface interface-id
Step 3
switchport mode {dynamic {auto |
desirable} | trunk}
Step 4
switchport access vlan vlan-id
Step 5
switchport trunk native vlan vlan-id
Step 6
end
Step 7
show interfaces interface-id switchport Display the switchport configuration of the interface in the
Step 8
show interfaces interface-id trunk
Step 9
copy running-config startup-config
OL-19808-01
A trunk port cannot be a secure port.
A trunk port cannot be a tunnel port.
Trunk ports can be grouped into EtherChannel port groups, but all trunks in the group must have the
same configuration. When a group is first created, all ports follow the parameters set for the first
port to be added to the group. If you change the configuration of one of these parameters, the switch
propagates the setting you entered to all ports in the group:
allowed-VLAN list.
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STP port priority for each VLAN.
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STP Port Fast setting.
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trunk status: if one port in a port group ceases to be a trunk, all ports cease to be trunks.
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We recommend that you configure no more than 24 trunk ports in PVST mode and no more than 40
trunk ports in MST mode.
Purpose
Enter global configuration mode.
Specify the port to be configured for trunking, and enter interface
configuration mode.
Configure the interface as a Layer 2 trunk (required only if the interface
is a Layer 2 access port or tunnel port or to specify the trunking mode).
(Optional) Specify the default VLAN, which is used if the interface stops
trunking.
Specify the native VLAN for IEEE 802.1Q trunks.
Return to privileged EXEC mode.
Administrative Mode and the Administrative Trunking Encapsulation
fields of the display.
Display the trunk configuration of the interface.
(Optional) Save your entries in the configuration file.
dynamic auto—Set the interface to a trunk link if the neighboring
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interface is set to trunk or desirable mode. This is the default.
dynamic desirable—Set the interface to a trunk link if the
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neighboring interface is set to trunk, desirable, or auto mode.
trunk—Set the interface in permanent trunking mode and negotiate
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to convert the link to a trunk link even if the neighboring interface is
not a trunk interface.
Catalyst 2360 Switch Software Configuration Guide
Configuring VLAN Trunks
9-17