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

Chapter 17 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:
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•
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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.
Supervisor Engine 6-E, Supervisor Engine 6L-E, Catalyst 4900M, Catalyst 4948E, Supervisor Engine
Note
7-E, and Supervisor Engine 7L-E only support dot1q encapsulation.
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 mode
{dynamic {auto | desirable} | trunk}
Step 4
Switch(config-if)# switchport access vlan
vlan_num
Step 5
Switch(config-if)# switchport trunk
native vlan vlan_num
Step 6
Switch(config-if)# switchport trunk
allowed vlan {add | except | all |
remove}
vlan_num[,vlan_num[,vlan_num[,....]]
OL-25340-01
Configuring an Ethernet Interface as a Layer 2 Trunk, page 17-5
Configuring an Interface as a Layer 2 Access Port, page 17-7
Clearing Layer 2 Configuration, page 17-8
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.
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.
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.
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.
Software Configuration Guide—Release IOS XE 3.3.0SG and IOS 15.1(1)SG
17-5