Cisco WS-C2980G-A Software Guide - Page 91

Chapter 6 Configuring Fast EtherChannel and Gigabit EtherChannel Understanding the LACP Table 6-2 EtherChannel Modes That Use LACP (continued) Mode passive (Default) active Description LACP mode that places a port into a passive negotiating state in which the port responds to LACP packets it receives but does not initiate LACP packet negotiation. LACP mode that places a port into an active negotiating state, in which the port initiates negotiations with other ports by sending LACP packets. LACP Parameters LACP uses the following parameters: • System priority Each switch running LACP must have a system priority. You can specify the system priority automatically or through the CLI (see the "Specifying the System Priority" section on page 6-19). The switch uses the MAC address and the system priority to form the system ID and is also used during negotiation with other systems. • Port priority Each port in the switch must have a port priority. You can specify the port priority automatically or through the CLI (see the "Specifying the Port Priority" section on page 6-19). The port priority and the port number form the port identifier. The switch uses the port priority to decide which ports to put in standby mode when a hardware limitation prevents all compatible ports from aggregating. • Administrative key Each port in the switch must have an administrative key value. You can specify the administrative key value automatically or through the CLI (see the "Specifying an Administrative Key Value" section on page 6-19). The administrative key defines the ability of a port to aggregate with other ports. The following factors determine a port's ability to aggregate with other ports: - Port physical characteristics, such as data rate, duplex capability, and point-to-point or shared medium - Configuration constraints that you establish When enabled, LACP always tries to configure the maximum number of compatible ports in a channel, up to the maximum allowed by the hardware (eight ports). If LACP is not able to aggregate all the ports that are compatible (for example, the remote system might have more restrictive hardware limitations), then the system places all the ports that cannot be actively included in the channel in hot standby state and uses them only if one of the channeled ports fails. You can configure different channels with ports that have been assigned the same administrative key. For example, if you assign eight ports to the same administrative key, you may configure four ports in a channel using LACP active mode and the remaining four ports in a manually configured channel using the on mode. An administrative key is meaningful only in the context of the switch that allocates it; there is no global significance to administrative key values. 78-15486-01 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 6-17