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Layer 3 Switching Software Feature and Configuration Guide
78-6235-04, Cisco IOS Release 12.0(10)W5(18)
Chapter 4 Configuring Interfaces
About Layer 3 Switching Interfaces
Step 3 Follow each interface command with the interface configuration commands required for your
particular interface.
The commands you enter define the protocols and applications that will run on the interface. The
commands are collected and applied to the interface command until you enter another interface
command, a command that is not an interface configuration command, or you enter end to return to
privileged EXEC mode.
Step 4 Check the status of the configured interface by using the EXEC show commands.
Router# show interface gigabitethernet 1/0/1
GigabitEthernet1/0/1 is up, line protocol is up
Hardware is K1 Gigabit Port, address is 00d0.ba1d.3207 (bia 00d0.ba1d.3207)
MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec, rely 255/255, load 1/255
Encapsulation ARPA, loopback not set, keepalive set (10 sec)
Full-duplex mode, 1000Mb/s, Auto-negotiation, 1000BaseSX
output flow-control is unsupported, input flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
About Layer 3 Switching Interfaces
Layer 3 switching supports two different Gigabit Ethernet interfaces, an eight-port module and a
two-port module. This section describes the initial configurations for both interface types.
Tips Before you configure interfaces, be sure to have the interface network (IP or IPX)
addresses and the corresponding subnet mask information. If you do not have this
information, consult your network administrator.
The Gigabit Ethernet interface modules can be configured as trunk ports, non-trunking ports, routed
ports, or bridged ports. The trunk ports employ 802.1Q encapsulation; Inter-Switch Link (ISL) is not
supported. You can use the Gigabit Ethernet ports as routed interfaces, or you can configure the ports
into a bridge group, which is the recommended configuration.
By configuring as many ports as possible in a bridge group, you can optimize the throughput of your
switch router. You can also ensure that your networks are routed by using integrated routing and
bridging features from Cisco IOS software. For configuration instructions, see the “About Integrated
Routing and Bridging” section on page 6-4.
Between ports on the eight-port Gigabit Ethernet interface module itself, local switching at Layer 2
provides nonblocking performance at wire speed. For ports on this module configured as a bridge group,
Layer 2 traffic is processed at full Gigabit Ethernet rates. For Layer 3 traffic, however, this interface
module provides 2-Gbps routing bandwidth from the switch fabric.