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Cisco Catalyst Blade Switch 3130 for Dell Software Configuration Guide
OL-13270-01
Chapter37 Configuring EtherChannels and Link-State Tracking
Configuring EtherChannels
To return EtherChannel load-balancing to the default configuration, us e t he no port-channel
load-balance global configuration command.
Configuring the PAgP Learn Method and Priority
Network devices are classified as PAgP physical learners or aggregate-port learners. A device is a
physical learner if it learns addresses by physical ports and directs transmissi ons ba sed o n that
knowledge. A device is an aggregate-port learner if it learns addresses by aggregate (logical) ports. The
learn method must be configured the same at both ends of the link.
When a device and its partner are both aggregate-port learners, they learn the address on the logical
port-channel. The device sends packets to the source by using any of the ports in the EtherChannel. With
aggregate-port learning, it is not important on which physical port the pack et arri ves.
PAgP cannot automatically detect when the partner device is a physical lea rner and when the local de vice
is an aggregate-port learner. Therefore, you must manually set the lea rn ing m e thod on the loc al device
to learn addresses by physical ports. You also must set the load-distribution method to source-based
distribution, so that any given source MAC address is always sent on the same physical port.
You also can configure a single port within the group for all transmissions and use other ports for hot
standby. The unused ports in the group can be swapped into operation in just a few seconds if the selected
single port loses hardware-signal detection. You can configure which port is always selected for packet
transmission by changing its priority with the pagp port-priority interface configuration command. The
higher the priority, the more likely that the port will be selected.
Note The switch supports address learning only on aggregate ports even though the physical-port keyword is
provided in the CLI. The pagp learn-method command and the pagp port-priority command have no
effect on the switch hardware, but they are required for PAgP interoperability with devices that only
support address learning by physical ports, such as the Catalyst 1900 sw itch .
When the link partner of the switch is a physical learner (such a s a Catal yst 1900 series switch), we
recommend that you configure the switch as a physical-port lea rn er by usi n g the pagp learn-metho d
physical-port interface configuration command. Set the load-distribution method based on the source
MAC address by using the port-channel load-balance src-mac global configuration command. The
switch then sends packets to the Catalyst 1900 switch using the same port in the EtherChannel from
which it learned the source address. Only use the pagp learn-method command in this situation.
Step3 end Return to privileged EXEC mode.
Step4 show etherchannel load-balance Verify your entries.
Step5 copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose