I got a pair of Catalyst 6509 series switches running on HSRP backing up each other, but recently we had a very weird problem.
Both the switches experienced hard lockup at the very same time and all connections were dropped.
We were unable to establish even the console connection. Hence we were forced to reboot both the switches.
As the switches were rebooted, no crash dumps could be recovered.
It is a one off incident.
For further investigation, we checked the access logs, SNMP traps, nothing was out of the ordinary. The configs were checked by a 3rd party support professional and deemed OK. None of the known IOS bugs was established to have caused the mentioned crash and I'll appreciate if anyone who has experienced the problem could shed some light.