Cisco Catalyst 4500 Series - Configuring Ethernet Interfaces for Layer 2 Switching

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.