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37-18
Catalyst 2960 and 2960-S Switch Software Configuration Guide
OL-8603-09
Chapter 37 Configuring EtherChannels and Link-State Tracking
Configuring EtherChannels
To return the priority to its default setting, use the no pagp port-priority interface configuration
command. To return the learning method to its default setting, use the no pagp learn-method interface
configuration command.
Configuring LACP Hot-Standby Ports
When enabled, LACP tries to configure the maximum number of LACP-compatible ports in a channel,
up to a maximum of 16 ports. Only eight LACP links can be active at one time. The software places any
additional links in a hot-standby mode. If one of the active links becomes inactive, a link that is in the
hot-standby mode becomes active in its place.
If you configure more than eight links for an EtherChannel group, the software automatically decides
which of the hot-standby ports to make active based on the LACP priority. To every link between systems
that operate LACP, the software assigns a unique priority made up of these elements (in priority order):
• LACP system priority
• System ID (the switch MAC address)
• LACP port priority
• Port number
In priority comparisons, numerically lower values have higher priority. The priority decides which ports
should be put in standby mode when there is a hardware limitation that prevents all compatible ports
from aggregating.
Determining which ports are active and which are hot standby is a two-step procedure. First the system
with a numerically lower system priority and system-id is placed in charge of the decision. Next, that
system decides which ports are active and which are hot standby, based on its values for port priority and
port number. The port-priority and port-number values for the other system are not used.
You can change the default values of the LACP system priority and the LACP port priority to affect how
the software selects active and standby links. For more information, see the “Configuring the LACP
System Priority” section on page 37-18 and the “Configuring the LACP Port Priority” section on
page 37-19.
Configuring the LACP System Priority
You can configure the system priority for all the EtherChannels that are enabled for LACP by using the
lacp system-priority global configuration command. You cannot configure a system priority for each
LACP-configured channel. By changing this value from the default, you can affect how the software
selects active and standby links.
You can use the show etherchannel summary privileged EXEC command to see which ports are in the
hot-standby mode (denoted with an H port-state flag).
Step 6
show running-config
or
show pagp channel-group-number internal
Verify your entries.
Step 7
copy running-config startup-config (Optional) Save your entries in the configuration file.
Command Purpose