Cisco WS-C4003 - Catalyst 4000 Chassis Switch Software Configuration Manual page 198

Disabling VLAN 1 on a Trunk Link
When a trunk port with VLAN 1 disabled becomes a nontrunk port, it is added to the native VLAN. If
the native VLAN is VLAN 1, the port is enabled and added to VLAN 1.
To disable VLAN 1 on a trunk interface, perform this task in privileged mode:
Task
Step 1
Disable VLAN 1 on the trunk interface.
Step 2
Verify the allowed VLAN list for the trunk.
This example shows how to disable VLAN 1 on a trunk link and verify the configuration:
Console> (enable) clear trunk 8/1 1
Removing Vlan(s) 1 from allowed list.
Port
Console> (enable) show trunk 8/1
Port
--------
8/1
Port
--------
8/1
Port
--------
8/1
99,1003,1005
Port
--------
8/1
003,1005
Console> (enable)
Software Configuration Guide—Catalyst 4000 Family, Catalyst 2948G, Catalyst 2980G, Releases 6.3 and 6.4
11-22
8/1 allowed vlans modified to 2-1005.
Mode Encapsulation
----------- -------------
on isl
Vlans allowed on trunk
---------------------------------------------------------------------
2-1005
Vlans allowed and active in management domain
---------------------------------------------------------------------
2-6,10,20,50,100,152,200,300,400,500,521,524,570,776,801-802,850,917,9
Vlans in spanning tree forwarding state and not pruned
---------------------------------------------------------------------
2-6,10,20,50,100,152,200,300,400,500,521,524,570,776,802,850,917,999,1
Chapter 11 Configuring VLAN Trunks on Fast Ethernet and Gigabit Ethernet Ports
Command
clear trunk mod_num/port_num [vlan-range]
show trunk [mod_num/port_num]
Status Native vlan
------------ -----------
trunking 1
78-12647-02