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10-5
Catalyst 3550 Multilayer Switch Software Configuration Guide
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Chapter 10 Configuring Interface Characteristics
Understanding Interface Types
Note
The SMI supports static routing and RIP; for more advanced routing, you must have the EMI installed
on your switch.
Configure routed ports by putting the interface into Layer 3 mode with the no switchport interface
configuration command. Then assign an IP address to the port, enable routing, and assign routing
protocol characteristics by using the ip routing and router protocol global configuration commands.
Caution
Entering a no switchport interface configuration command shuts the interface down and then re-enables
it, which might generate messages on the device to which the interface is connected.
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. For more information about feature
combinations, see the
“Optimizing System Resources for User-Selected Features” section on page 7-27
For more information about IP unicast and multicast routing and routing protocols, see
“Configuring IP Unicast Routing”
Chapter 34, “Configuring IP Multicast Routing.”
EtherChannel Port Groups
EtherChannel port groups provide the ability to treat multiple switch ports as one switch port. These port
groups act as a single logical port for high-bandwidth connections between switches or between switches
and servers. An EtherChannel balances the traffic load across the links in the channel. If a link within
the EtherChannel fails, traffic previously carried over the failed link changes to the remaining links. You
can group multiple trunk ports into one logical trunk port, group multiple access ports into one logical
access port, group multiple tunnel ports into one logical tunnel port, or group multiple routed ports into
one logical routed port. Most protocols operate over either single ports or aggregated switch ports and
do not recognize the physical ports within the port group. Exceptions are the DTP, the Cisco Discovery
Protocol (CDP), and the Port Aggregation Protocol (PAgP), which operate only on physical ports.
When you configure an EtherChannel, you create a port-channel logical interface and assign an interface
to the EtherChannel. For Layer 3 interfaces, you manually create the logical interface by using the
interface port-channel global configuration command. For Layer 2 interfaces, the logical interface is
dynamically created. For both Layer 3 and 2 interfaces, you manually assign an interface to the
EtherChannel by using the channel-group interface configuration command. This command binds the
physical and logical ports together. For more information, see
Connecting Interfaces
Devices within a single VLAN can communicate directly through any switch. Ports in different VLANs
cannot exchange data without going through a routing device or routed interface.
With a standard Layer 2 switch, ports in different VLANs have to exchange information through a router.
In the configuration shown in
, when Host A in VLAN 20 sends data to Host B in VLAN 30,
it must go from Host A to the switch, to the router, back to the switch, and then to Host B.