EtherChannel

The adapters that belong to an EtherChannel must be connected to the same EtherChannel-enabled switch. If the adapters are connected to different switches, those switches must be stacked and act as a single switch.

You must manually configure this switch to treat the ports that belong to the EtherChannel as an aggregated link. Your switch documentation might refer to this capability as link aggregation or trunking.

For EtherChannel to work correctly, the link polling mechanism that periodically verifies the status of the link must be enabled on each adapter before the EtherChannel is created. Traffic is distributed across the adapters in either the standard way (where the adapter over which the packets are sent is chosen depending on an algorithm) or on a round-robin basis (where packets are sent evenly across all adapters). Incoming traffic is distributed in accordance to the switch configuration and is not controlled by the EtherChannel operation mode.

You can configure multiple EtherChannels per system. If all links in one EtherChanel are attached to a single switch and if the switch is unplugged or fails, the entire EtherChannel is lost. To solve this problem, a backup option is available that keeps the service active when the main EtherChannel fails. The backup and EtherChannel adapters must be attached to different network switches, which must be interconnected for this setup to work properly. If all adapters in the EtherChannel fail, the backup adapter is used to send and receive all traffic. When any link in the EtherChannel is restored, the service is moved back to the EtherChannel.

For example, ent0 and ent1 can be configured as the main EtherChannel adapters, and ent2 as the backup adapter, creating an EtherChannel called en3. Ideally, ent0 and ent1 are connected to the same EtherChannel-enabled switch, and ent2 is connected to a different switch. In this example, all traffic sent over en3 (the interface of EtherChannel) is sent over ent0 or ent1 by default (depending on the packet distribution scheme of EtherChannel), whereas ent2 is idle. If at any time both ent0 and ent1 fail, all traffic is sent over the backup adapter ent2. When either ent0 or ent1 recover, they are again used for all traffic.

Network Interface Backup, a mode of operation available for EtherChannel, protects against a single point of Ethernet network failure. No special hardware is required to use Network Interface Backup, but the backup adapter must be connected to a separate switch for maximum reliability. In Network Interface Backup mode, only one adapter at a time is actively used for network traffic. The EtherChannel tests the currently active adapter and, optionally, the network path to a user-specified node. When a failure is detected, the next adapter will be used for all traffic. Network Interface Backup provides detection and failover with no disruption to user connections. Network Interface Backup was originally implemented as a mode in the EtherChannel system management interface tool (SMIT) menu. The backup adapter provides the equivalent function, so the mode was eliminated from the SMIT menu. To configure network interface backup, see Network Interface Backup configuration.