APA - failover

[Andi Rigauer]

Hi experts,

one question , whatr triggers APA to make a failover of the IP?
I already read the man and didn't found some deep details.
So which layer is monitored and when occures a failover?
Thanks in advance
Andi

[Dietmar Konermann]

LINK DOWN and UP events from the driver trigger it. The LAN Manager adds polling on link level to improve the reliability of the fault detection (similar to the mechanisms ServiceGuard uses).

Best regards...
Dietmar.

[Ajit Natarajan]

Dietmar is correct in that link down events will trigger a failover.

Please note the following:

1. Link failover will happen if the failover group is configured with hot standby (manual) or LAN monitor mode.

2. LAN monitor mode will additionally use ``heartbeat'' packets to check that the primary and/or backup links are functional. Hot standby mode will not use such packets and relies exclusively on link down/up.

3. Under normal circumstances, when the primary comes back up, failback will occur.

4. In hot standby mode, since link up is exclusively used for failback, spanning tree may not have completed on the switch port connected to the primary. This is a known issue of ``failback too fast''. Since LAN monitor additionally uses ``hearbeat'' packets, this is not an issue in LAN monitor mode.

5. HP recommends LAN monitor over hot standby for the reasons above.

Thanks.

Ajit
HP Gigabit Ethernet