Administrator Guide

For information about enabling and conguring the Spanning Tree Protocol, refer to Spanning Tree Protocol (STP).
To view the interfaces in Layer 2 mode, use the show interfaces switchport command in EXEC mode.
Conguring Layer 3 (Network) Mode
When you assign an IP address to a physical interface, you place it in Layer 3 mode.
To enable Layer 3 mode on an individual interface, use the following commands. In all interface types except VLANs, the shutdown
command prevents all trac from passing through the interface. In VLANs, the shutdown command prevents Layer 3 trac from passing
through the interface. Layer 2 trac is unaected by the shutdown command. One of the interfaces in the system must be in Layer 3
mode before you congure or enter a Layer 3 protocol mode (for example, OSPF).
• Enable Layer 3 on an individual interface
INTERFACE mode
ip address
• Enable the interface.
INTERFACE mode
no shutdown
Example of Error Due to Issuing a Layer 3 Command on a Layer 2 Interface
If an interface is in the incorrect layer mode for a given command, an error message is displayed (shown in bold). In the following example,
the ip address command triggered an error message because the interface is in Layer 2 mode and the ip address command is a
Layer 3 command only.
Dell(conf-if)#show config
!
interface TengigabitEthernet 1/2
no ip address
switchport
no shutdown
Dell(conf-if)#ip address 10.10.1.1 /24
% Error: Port is in Layer 2 mode Te 1/2.
Dell(conf-if)#
To determine the conguration of an interface, use the show config command in INTERFACE mode or the various show interface
commands in EXEC mode.
Conguring Layer 3 (Interface) Mode
To assign an IP address, use the following commands.
• Enable the interface.
INTERFACE mode
no shutdown
• Congure a primary IP address and mask on the interface.
INTERFACE mode
ip address ip-address mask [secondary]
The ip-address must be in dotted-decimal format (A.B.C.D) and the mask must be in slash format (/xx).
Add the keyword secondary if the IP address is the interface’s backup IP address.
Example of the show ip interface Command
You can only congure one primary IP address per interface. You can congure up to 255 secondary IP addresses on a single interface.
450
Interfaces