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 that is made up of these elements (in priority order): • LACP system priority • System ID (the device 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.
(Optional) Configuring the Link Aggregation Control Protocol Max Bundle When you specify the maximum number of bundled LACP ports allowed in a port channel, the remaining ports in the port channel are designated as hot-standby ports. Beginning in privileged EXEC mode, follow these steps to configure the maximum number of LACP ports in a port channel. Procedure Configuring EtherChannels (Optional) Configuring the Link Aggregation Control Protocol Max Bundle Command or Action Purpose Step 1 enable Example: Device> enable Enables privileged EXEC mode. Enter your password if prompted. Step 2 configure terminal Example: Device# configure terminal Enters global configuration mode.
Step 3 interface port-channel channel-number Example: Device(config)# interface port-channel 2 Enters interface configuration mode for a port channel. For channel-number, the range is 1 to 128. Step 4 lacp max-bundle max-bundle-number Example: Device(config-if)# lacp max-bundle 3 Specifies the maximum number of LACP ports in the port-channel bundle. The range is 1 to 8. Configuring EtherChannels 21