Anyone done this? More to the point; anyone got a procedure? AIX5.1 on p690.

I use this frequently.
smit etherchannel
choose Add An EtherChannel / Link Aggregation
choose the adapter for the main link
choose the Backup Adapter


That's all, it will create ent8 (for instance).
then smit tcpip, minimum configuration, and configure ent8.

When it's configured, if you want to test it, ping a system, see where the lights react on your Ether swith, remove the cable, you will see an error message at the console and you will see the lamp start blinking on the backup adapter cable.

We use etherchannel in backup mode (as zorba suggested) as a standard around here. Provides an extra layer of redundancy, and also an extra headache if you don't do it right. Though, one thing zorba didn't mention, if you do use the NIC backup option make sure your cables go to different switches. If they don't and you lose a switch you'll lose your network connection.

+1 : You're fully right, Loosecannon : it's wiser to plug the backup adapter to a different Ethernet switch. Because the guy who will happen to grasp the main cable while falling down will make the main Ethernet switch unusable (that's the Murphy Law).