Configuring Ethernet Interfaces For Layer 2 Switching - Cisco Catalyst 4500 Series Software Configuration Manual

Chapter 19 Configuring Layer 2 Ethernet Interfaces

Configuring Ethernet Interfaces for Layer 2 Switching

The following sections describe how to configure Layer 2 switching on a Catalyst 4500 series switch
switch:
•
•
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Configuring an Ethernet Interface as a Layer 2 Trunk
The default for Layer 2 interfaces is switchport mode dynamic auto. If the neighboring interface
Note
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
Step 1
Switch(config)# interface {fastethernet |
gigabitethernet | tengigabitethernet}
slot/port
Step 2
Switch(config-if)# shutdown
Step 3
Switch(config-if)# switchport trunk
encapsulation {dot1q | negotiate}
Step 4
Switch(config-if)# switchport mode
{dynamic {auto | desirable} | trunk}
Step 5
Switch(config-if)# switchport access vlan
vlan_num
Step 6
Switch(config-if)# switchport trunk
native vlan vlan_num
Step 7
Switch(config-if)# switchport trunk
allowed vlan {add | except | all |
remove}
vlan_num[,vlan_num[,vlan_num[,....]]
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
Catalyst 4500 Series Switch, Cisco IOS Software Configuration Guide - Cisco IOS XE 3.9.xE and IOS 15.2(5)Ex
Configuring Ethernet Interfaces for Layer 2 Switching
Purpose
Specifies the interface to configure.
(Optional) Shuts down the interface to prevent traffic flow until
configuration is complete.
(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).
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.)
(Optional) Specifies the access VLAN, which is used if the
interface stops trunking. The access VLAN is not used as the
native VLAN.
The vlan_num parameter is either a single VLAN number
Note
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.
For 802.1Q trunks, specifies the native VLAN.
If you do not set the native VLAN, the default is used
Note
(VLAN 1).
(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.
19-5