Etherchannel Port Groups; Connecting Interfaces - Cisco WS-C3560-48PS-S Software Configuration Manual

Chapter 10 Configuring Interface Characteristics

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, 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. Then you manually assign an interface to the
EtherChannel by using the channel-group interface configuration command. For Layer 2 interfaces, use
the channel-group interface configuration command to dynamically create the port-channel logical
interface. This command binds the physical and logical ports together. For more information, see
Chapter 29, "Configuring EtherChannels."

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. With a standard Layer 2 switch, ports in
different VLANs have to exchange information through a router. In the configuration shown in
Figure
switch, to the router, back to the switch, and then to Host B.
Figure 10-1 Connecting VLANs with Layer 2 Switches
By using the switch with routing enabled, when you configure VLAN 20 and VLAN 30 each with an
SVI to which an IP address is assigned, packets can be sent from Host A to Host B directly through the
switch with no need for an external router
78-16156-01
10-1, when Host A in VLAN 20 sends data to Host B in VLAN 30, it must go from Host A to the
Host A
VLAN 20
Cisco router
Switch
Host B
VLAN 30
(Figure 10-2).
Catalyst 3560 Switch Software Configuration Guide
Understanding Interface Types
10-5