AIX Tip of the Week

New AIX Hot Spare Network Adapter Functionality

Audience: System Administrators

Date: May 25, 2001

AIX 4.3.3 ML 8 and AIX V5 support "hot spare" network adapters without HACMP. The attached note from Steve Pittman describes the function in greater detail

The AIX Differences Guide that Steve refers to can be found at (search for "AIX")


A new function called Network Interface Takeover ships with AIX V4.3.3 Maintenance Level 8. The function is also available in AIX V5.

The function adds a netif_backup choice to the Mode option on the Add An Etherchannel smit menu, which allows an AIX sysadmin to configure a pair of adapters in active/standby mode. That is, one adapter is active and the other is an idle standby. If the active adapter fails, the Ethernet device driver will activate the idle standby adapter, take over the failed adapter's IP and MAC address, and allow TCP/IP applications to continue without interruption.

The AIX 5L Differences Guide Version 5.1 Edition Redbook (SG24-5765-01) says:

Etherchannel is a network aggregation technology that allows you to produce a single large pipe by combining the bandwidth of multiple Ethernet adapters. In AIX 5L Version 5.1, the Etherchannel feature has been enhanced to support the detection of interface failures. This is called network interface backup.

In the network interface backup mode, the channel will only activate one adapter at a time. The intention is that the adapters are plugged into different Ethernet switches, each of which is capable of getting to any other machine on the subnet/network. When a problem is detected, either with the direct connection, or through inability to ping a machine, the channel will deactivate the current adapter, and activate a backup adapter.

The network interface backup feature is currently supported by 10/100 Ethernet and gigabit Ethernet PCI cards (devices.pci.23100020.rte and devices.pci.14100401.rte). If you are using other devices, you might get unexpected results.

The Differences Guide has some additional information about configuring Etherchannel for network interface backup.

See the AIX Version 4.3 Differences Guide Redbook (SG24-2014-02) for more information about basic Cisco EtherChannel support (without Network Interface Takeove) in AIX V4.3.3.



IBM Open Systems Technology Team - Dept. IGRF
San Ramon, Ca.
I intend to *MAKE* the system work!

Bruce Spencer,