28-18
Cisco ME 3800X and 3600X Switch Software Configuration Guide
OL-23400-01
Chapter 28 Configuring EtherChannels
Configuring EtherChannels
Ports are considered for active use in aggregation in link-priority order starting with the port attached to
the highest priority link. Each port is selected for active use if the preceding higher priority selections
can also be maintained. Otherwise, the port is selected for standby mode.
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 28-18
and the
“Configuring the LACP Port Priority” section on
page 28-18
.
Configuring the LACP System Priority
You can configure the system priority for all of 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).
Beginning in privileged EXEC mode, follow these steps to configure the LACP system priority. This
procedure is optional.
To return the LACP system priority to the default value, use the no lacp system-priority global
configuration command.
Configuring the LACP Port Priority
By default, all ports use the same port priority. If the local system has a lower value for the system
priority and the system ID than the remote system, you can affect which of the hot-standby links become
active first by changing the port priority of LACP EtherChannel ports to a lower value than the default.
The hot-standby ports that have lower port numbers become active in the channel first. 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).
Note
If LACP is not able to aggregate all the ports that are compatible (for example, the remote system might
have more restrictive hardware limitations), all the ports that cannot be actively included in the
EtherChannel are put in the hot-standby state and are used only if one of the channeled ports fails.
Command
Purpose
Step 1
configure terminal
Enter global configuration mode.
Step 2
lacp system-priority priority
Configure the LACP system priority.
For priority, the range is 1 to 65535. The default is 32768.
The lower the value, the higher the system priority.
Step 3
end
Return to privileged EXEC mode.
Step 4
show running-config
or
show lacp sys-id
Verify your entries.
Step 5
copy running-config startup-config
(Optional) Save your entries in the configuration file.
