Cisco Catalyst 4500 Series, Software Configuration Manual

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19-5
Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.xE and IOS 15.2(5)Ex
Chapter 19 Configuring Layer 2 Ethernet Interfaces
Configuring Ethernet Interfaces for Layer 2 Switching
Configuring Ethernet Interfaces for Layer 2 Switching
The following sections describe how to configure Layer 2 switching on a Catalyst 4500 series switch
switch:
•
Configuring an Ethernet Interface as a Layer 2 Trunk, page 19-5
• Configuring an Interface as a Layer 2 Access Port, page 19-7
•
Clearing Layer 2 Configuration, page 19-8
Configuring an Ethernet Interface as a Layer 2 Trunk
Note
The default for Layer 2 interfaces is switchport mode dynamic auto . If the neighboring interface
supports trunking and is configured to trunk mode or dynamic desirable mode, the link becomes a
Layer 2 trunk.
To configure an interface as a Layer 2 trunk, perform this task:
Command Purpose
Step 1
Switch(config)# interface { fastethernet |
gigabitethernet | tengigabitethernet }
slot / port
Specifies the interface to configure.
Step 2
Switch(config-if)# shutdown
(Optional) Shuts down the interface to prevent traffic flow until
configuration is complete.
Step 3
Switch(config-if)# switchport trunk
encapsulation { dot1q | negotiate }
(Optional) Specifies the encapsulation.
Note
You must enter this command with the dot1q keyword to
support the switchport mode trunk command, which is
not supported by the default mode ( negotiate ).
Step 4
Switch(config-if)# switchport mode
{ dynamic { auto | desirable } | trunk }
Configures the interface as a Layer 2 trunk. (Required only if the
interface is a Layer 2 access port or to specify the trunking mode.)
Step 5
Switch(config-if)# switchport access vlan
vlan_num
(Optional) Specifies the access VLAN, which is used if the
interface stops trunking. The access VLAN is not used as the
native VLAN.
Note
The vlan_num parameter is either a single VLAN number
from 1 to 1005 or a range of VLANs described by two
VLAN numbers, the lesser one first, separated by a dash.
Do not enter any spaces between comma-separated
vlan
parameters or in dash-specified ranges.
Step 6
Switch(config-if)# switchport trunk
native vlan vlan_num
For 802.1Q trunks, specifies the native VLAN.
Note If you do not set the native VLAN, the default is used
(VLAN 1).
Step 7
Switch(config-if)# switchport trunk
allowed vlan { add | except | all |
remove }
vlan_num [, vlan_num [, vlan_num [,....]]
(Optional) Configures the list of VLANs allowed on the trunk. All
VLANs are allowed by default. You cannot remove any of the
default VLANs from a trunk.