should_drop_message / attack replay attempted - Error Heartbeat
If you have cloned your heartbeat Server to get another failover machine and you get following Errors:
Feb 15 21:05:10 machine1 heartbeat: : ERROR: should_drop_message: attempted replay attack [machine2]? [gen = 1275513319, curgen = 1275513320]
Remove hb_generation and hb_uuid file from /var/lib/heartbeat then restart HA service at both machine.
sudo rm /var/lib/heartbeat/hb_uuid
sudo rm /var/lib/heartbeat/hb_generation
sudo /etc/init.d/heartbeat restart