Interaction With Other Features; Configuring A Trunk Port - Cisco 2950 - Catalyst Switch Configuration Manual

Configuring VLAN Trunks

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 an 802.1Q 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 Administrative
Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
17-18
A trunk port cannot be a secure 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 that you entered to all ports in the group:
allowed-VLAN list
–
STP port priority for each VLAN
–
STP Port Fast setting
–
– trunk status (If one port in a port group ceases to be a trunk, all ports cease to be trunks.)
If you try to enable 802.1X on a trunk port, an error message appears, and 802.1X is not enabled. If
you try to change the mode of an 802.1X-enabled port to trunk, the port mode is not changed.
A port in dynamic mode can negotiate with its neighbor to become a trunk port. If you try to enable
802.1X on a dynamic port, an error message appears, and 802.1X is not enabled. If you try to change
the mode of an 802.1X-enabled port to dynamic, the port mode is not changed.
Protected ports are supported on 802.1Q trunks.
Purpose
Enter global configuration mode.
Enter the interface configuration mode and the port to be configured for
trunking.
Configure the interface as a Layer 2 trunk (required only if the interface
is a Layer 2 access port or to specify the trunking mode).
(Optional) Specify the default VLAN, which is used if the interface stops
trunking.
Specify the native VLAN.
Return to privileged EXEC mode.
Mode and the Administrative Trunking Encapsulation fields of the
display.
• dynamic auto—Set the interface to a trunk link if the neighboring
interface is set to trunk or desirable mode.
• dynamic desirable—Set the interface to a trunk link if the
neighboring interface is set to trunk, desirable, or auto mode.
• trunk—Set the interface in permanent trunking mode and negotiate
to convert the link to a trunk link even if the neighboring interface is
not a trunk interface.
Chapter 17 Configuring VLANs
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