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Cisco IE 2000 Switch Software Configuration Guide
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Chapter 40 Configuring EtherChannels
Information About Configuring EtherChannels
With source-and-destination IP address-based forwarding, packets are sent to an Ether Channel and
distributed across the EtherChannel ports, based on both the source and destination IP a ddresses of the
incoming packet. This forwarding method, a combination of source-IP and destinati on-IP address-based
forwarding, can be used if it is not clear whether source-IP or destination-IP address-based forwarding
is better suited on a particular switch. In this method, packets sent from the IP address A to IP address
B, from IP address A to IP address C, and from IP address C to IP address B could all us e different ports
in the channel.
Different load-balancing methods have different advantages, and the choice of a particular
load-balancing method should be based on the position of the switch in the network and the kind of
traffic that needs to be load-distributed. In Figure 40-3, an EtherChannel from a switch that is
aggregating data from four workstations communicates with a router. Because the router is a
single-MAC-address device, source-based forwarding on the switch EtherChannel ensures that the
switch uses all available bandwidth to the router. The router is configured for destination-based
forwarding because the large number of workstations ensures that the traffic is evenly distributed from
the router EtherChannel.
Use the option that provides the greatest variety in your configuration. For example, if the traffic on a
channel is only going to a single MAC address, using the destination-MAC address always chooses the
same link in the channel. Using source addresses or IP addre sses might result in better load balancing.
Figure 40-3 Load Distribution and Forwarding Methods
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Cisco router
with destination-based
forwarding enabled
EtherChannel
Switch with
source-based
forwarding enabled