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Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter8 Configuring Interface Characteristics
Configuring Layer 3 Interfaces
To verify that an interface is disabled, enter the show inte rfaces privileged EXEC command. A disabled
interface is shown as administratively down in the show interface command display as with Gigabit
Ethernet interface 0/1 in this example.
Switch# show interfaces
<output truncated>
GigabitEthernet0/2 is administratively down, line protocol is down
Hardware is Gigabit Ethernet, address is 0002.4b29.4403 (bia 0002.4b29.4403)
MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Auto-duplex, Auto-speed
<output truncated>
Configuring Layer 3 Interfaces
The Catalyst 3550 with the enhanced multilayer software image supports three 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 t he interface vlan global configuration command. To
delete an SVI, use the no interface vlan global configuration command.
For information about assigning Layer 2 ports to VLANs, see Chapter 9, “Creating and Maintaining
VLANs.”
•Layer 3 EtherChannel ports: EtherChannel interfaces made up of routed ports.
EtherChannel port interfaces are described in Chapter 21, “Configuri ng Eth erC hann el. ”
•Routed ports: Routed ports are physical ports configured to b e i n La yer 3 m ode b y u sing th e no
switchport interface configuration command.
Note A Layer 3 switch can have an IP address assigned to each routed port and SVI. The num ber of ro uted
ports and SVIs that you can configure is not limited by softw are ; ho weve r, the interr ela tio nship
between this number and the number of other features being configured might have an impact on
CPU utilization because of hardware limitations. For more information ab out feature combinations,
see the “Optimizing System Resources for User-Selected Features” section on page6-57.
All Layer 3 interfaces require an IP address to route traffic. The following procedure shows how to
configure an interface as a Layer 3 interface and how to assign an IP addresses to an interface.
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 re-enables the interface, which might generate messages on the de vice 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.