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Cisco Systems Intelligent Gigabit Ethernet Switch Modules for the IBM BladeCenter, Software Configuration Guide
24R9746
Chapter 24 Configuring EtherChannels and Layer 2 Trunk Failover
Understanding EtherChannels
Figure 24-3 Load Distribution and Forwarding Methods
With source-and-destination MAC address forwarding, packets forwarded to an EtherChannel are
distributed across the ports in the channel based on both the source and destination MAC addresses. This
combination forwarding method can be used if it is not clear whether source-MAC or destination-MAC
address forwarding is better suited on a particular switch.
With source-IP address-based forwarding, packets forwarded to an EtherChannel are distributed across
the ports in the EtherChannel based on the source-IP address of the incoming packet. Therefore, to
provide load-balancing, packets from different IP addresses use different ports in the channel, but
packets from the same IP address use the same port in the channel.
With destination-IP address-based forwarding, packets forwarded to an EtherChannel are distributed
across the ports in the EtherChannel based on the destination-IP address of the incoming packet.
Therefore, to provide load-balancing, packets from the same IP source address sent to different IP
destination addresses could be sent on different ports in the channel. But packets sent from different
source-IP addresses to the same destination-IP address are always sent on the same port in the channel.
With source-and-destination IP address-based forwarding, packets forwarded to an EtherChannel are
distributed across the ports in the EtherChannel based on both the source and destination IP addresses
of the incoming packet. This combination forwarding method can be used if it is not clear whether
source-IP or destination-IP address-based forwarding is better suited on a particular switch.
Use the option that provides the greatest variety in your configuration. For example, if the traffic on a
channel is going only to a single MAC address, using the destination-MAC address always chooses the
same link in the channel. Using source addresses or IP addresses might result in better load balancing.
BladeCenter
92433
Cisco router
with destination-based
forwarding enabled
EtherChannel