Reference Guide

Spanning Tree Protocol (STP) | 875
Configuring Interfaces for Layer 2 Mode
All interfaces on all switches that will participate in Spanning Tree must be in Layer 2 mode and enabled.
Figure 45-1. Example of Configuring Interfaces for Layer 2 Mode
To configure the interfaces for Layer 2 and then enable them:
Verify that an interface is in Layer 2 mode and enabled using the
show config command from INTERFACE
mode.
Figure 45-2. Verifying Layer 2 Configuration
Step Task Command Syntax Command Mode
1 If the interface has been assigned an IP address,
remove it.
no ip address INTERFACE
2 Place the interface in Layer 2 mode. switchport INTERFACE
3 Enable the interface. no shutdown INTERFACE
R1
R2
R3
1/3
3/1
3/2
3/4
3/3
1/4
1/1 1/2
2/1
2/2
2/3
2
/4
R1(conf)# int range gi 1/1 - 4
R1(conf-if-gi-1/1-4)# switchport
R1(conf-if-gi-1/1-4)# no shutdown
R1(conf-if-gi-1/1-4)#show config
!
interface GigabitEthernet 1/1
no ip address
switchport
no shutdown
!
interface GigabitEthernet 1/2
no ip address
switchport
no shutdown
!
interface GigabitEthernet 1/3
no ip address
switchport
no shutdown
!
interface GigabitEthernet 1/4
no ip address
switchport
no shutdown
FTOS(conf-if-gi-1/1)#show config
!
interface GigabitEthernet 1/1
no ip address
switchport
no shutdown
FTOS(conf-if-gi-1/1)#
Indicates that the interface is in Layer 2 mode