16- and 36-Port Ethernet Switch Module for Cisco 2600 Series, Cisco 3600 Series, and Cisco 3700 Series
Configuration Tasks
120
Cisco IOS Release 12.2(2)XT, 12.2(8)T, and 12.2(15)ZJ
Configuring Layer 3 Interfaces
The Ethernet switch network module supports two types of Layer 3 interfaces for routing and bridging:
•
SVIs: You should configure SVIs for any VLANs for which you want to route traffic. SVIs are
created when you enter a VLAN ID following the interface vlan global configuration command. To
delete an SVI, use the no interface vlan global configuration command.
•
Routed ports: Routed ports are physical ports configured to be in Layer 3 mode by using the no
switchport interface configuration command.
Note
A Layer 3 switch can have an IP address assigned to each routed port and SVI. The number of routed
ports and SVIs that you can configure is not limited by software; however, the interrelationship
between this number and the number of other features being configured might have an impact on
CPU utilization because of hardware limitations.
All Layer 3 interfaces require an IP address to route traffic (a routed port cannot obtain an IP address
from a DHCP server, but the router can act as a DHCP server and serve IP addresses through a routed
port). The following procedure shows how to configure an interface as a Layer 3 interface and how to
assign an IP addresses to an interface.
Routed ports support only CEF switching (IP fast switching is not supported).
Note
If the physical port is in Layer 2 mode (the default), you must enter the no switchport interface
configuration command to put the interface into Layer 3 mode. Entering a no switchport command
disables and then reenables the interface, which might generate messages on the device to which the
interface is connected. When you use this command to put the interface into Layer 3 mode, you are
also deleting any Layer 2 characteristics configured on the interface. (Also, when you return the
interface to Layer 2 mode, you are deleting any Layer 3 characteristics configured on the interface.)
Beginning in privileged EXEC mode, follow these steps to configure a Layer 3 interface:
To remove an IP address from an interface, use the no ip address interface configuration command.
Command
Purpose
Step 1
configure terminal
Enters global configuration mode.
Step 2
interface {{fastethernet | gigabitethernet} interface-id}
| {vlan vlan-id} | {port-channel port-channel-number}
Enters interface configuration mode, and enter the
interface to be configured as a Layer 3 interface.
Step 3
no switchport
For physical ports only, enters Layer 3 mode.
Step 4
ip address ip-address subnet-mask
Configures the IP address and IP subnet.
Step 5
no shutdown
Activates the interface. (Required only if you shut down
the interface.)
Step 6
end
Returns to privileged EXEC mode.
Step 7
show interfaces [interface-id]
show ip interface [interface-id]
show running-config interface [interface-id]
Verifies the configuration.
Step 8
copy running-config startup-config
(Optional) Saves your entries in the configuration file.