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Catalyst 6500 Series Switch Software Configuration Guide—Release 8.7
OL-8978-04
Chapter 5 Configuring Ethernet VLAN Trunks
Configuring a Trunk Link
In software releases prior to software release 8.3(1), to define the allowed VLANs list for a trunk port,
perform this task in privileged mode:
This example shows how to define the allowed VLANs list to allow VLANs 1–100, VLANs 500–1005,
and VLAN 2500 on trunk port 1/1 and verify the allowed VLAN list for the trunk:
Console> (enable)
clear trunk 1/1 101-499
Removing Vlan(s) 101-499 from allowed list.
Port 1/1 allowed vlans modified to 1-100,500-1005.
Console> (enable)
set trunk 1/1 2500
Adding vlans 2500 to allowed list.
Port(s) 1/1 allowed vlans modified to 1-100,500-1005,2500.
Console> (enable)
show trunk 1/1
Port Mode Encapsulation Status Native vlan
-------- ----------- ------------- ------------ -----------
1/1 desirable isl trunking 1
Port Vlans allowed on trunk
-------- ---------------------------------------------------------------------
1/1 1-100, 500-1005,2500
Port Vlans allowed and active in management domain
-------- ---------------------------------------------------------------------
1/1 1,521-524
Port Vlans in spanning tree forwarding state and not pruned
-------- ---------------------------------------------------------------------
1/1 1,521-524
Console> (enable)
In software release 8.3(1) and later releases, if you want to configure a trunk but do not want to allow
any VLANs on the trunk, enter the
none
keyword as follows:
Console> (enable)
set trunk 7/1 on none dot1q
Removing Vlan(s) 1-4094 from allowed list.
Port 7/1 allowed vlans modified to none.
Port(s) 7/1 trunk mode set to on.
Port(s) 7/1 trunk type set to dot1q.
Console> (enable)
Disabling a Trunk Port
To turn off trunking on a port, perform this task in privileged mode:
Task
Command
Step 1
Remove VLANs from the allowed VLANs list for
a trunk.
clear trunk
mod/port
vlans
Step 2
(Optional) Add specific VLANs to the allowed
VLANs list for a trunk.
set trunk
mod/port
vlans
Step 3
Verify the allowed VLANs list for the trunk.
show trunk
[
mod/port
]
Task
Command
Step 1
Turn off trunking on a port.
set trunk
mod/port
off
Step 2
Verify the trunking configuration.
show trunk
[
mod/port
]