Cisco Catalyst 2950 Command Reference Manual page 538

switchport trunk
•
Defaults VLAN 1 is the default native VLAN ID on the port.
The default for all VLAN lists is to include all VLANs.
Command Modes Interface configuration
Command History Release
12.1(6)EA2
12.1(14)EA1
Usage Guidelines A trunk port cannot be a secure port or a monitor port. However, a static-access port can monitor a
VLAN on a trunk port. The VLAN monitored is the one associated with the static-access port.
Allowed VLAN:
•
•
Native VLANs:
•
Catalyst 2950 and Catalyst 2955 Switch Command Reference
2-510
vlan-atom is either a single VLAN number from 1 to 4094, a list of nonconsecutive VLANs, or a
continuous range of VLANs described by two VLAN numbers, the lower one first, separated by a
hyphen.
For a list of nonconsecutive VLAN IDs, separate the VLAN IDs with a comma. Do not enter a space
after the comma.
For a continuous range of VLAN IDs, use a hyphen to designate the range. Do not enter a space
before or after the hyphen.
These are examples showing how to specify one or more VLANs:
Single VLAN—101
–
List of nonconsecutive VLANs—10,12,14,16,18
–
Continuous range of VLANs—10-15
–
– List of VLAN continuous ranges—10-15,20-24
– List of nonconsecutive VLANs and VLAN continuous ranges—8,11,20-24,44
Modification
This command was introduced.
The allowed vlan vlan list add, remove, and except keywords were
modified to accept the VLAN 1 and VLANs 1002 to 1005 values.
To reduce the risk of spanning-tree loops or storms, you can disable VLAN 1 on any individual
VLAN trunk port by removing VLAN 1 from the allowed list. This is known as VLAN 1
minimization. VLAN 1 minimization disables VLAN 1 (the default VLAN on all Cisco switch trunk
ports) on an individual VLAN trunk link. As a result, no user traffic, including spanning-tree
advertisements, is sent or received on VLAN 1.
When you remove VLAN 1 from a trunk port, the interface continues to send and receive
management traffic, for example, Cisco Discovery Protocol (CDP), Port Aggregation Protocol
(PAgP), Link Aggregation Control Protocol (LACP), Dynamic Trunking Protocol (DTP), and
VLAN Trunking Protocol (VTP) in VLAN 1.
The no form of the allowed vlan command resets the list to the default list, which allows all VLANs.
All untagged traffic received on an IEEE 802.1Q trunk port is forwarded with the native VLAN
configured for the port.
Chapter 2 Catalyst 2950 and 2955 Cisco IOS Commands
0L-10102-01