497 - The number of the IT beast
anthonyv 2000004B9K Visits (31677)
I recently had a client ask me if I had seen this problem in Cisco Device manager: Device Manager was showing them 100% utilisation for CPU on one of their MDS9509s. I had a look at the show tech-support and curiously show process cpu showed practically no CPU usage at all. I suggested a display problem and sure enough, Cisco confirmed it:
CSCte81951 Symptom: The show system resources command shows high CPU usage even when there is not
Curiously the Cisco tech support person stated that in fact a CP switchover every 497 days would prevent the issue reoccurring. This is curious because 248 days is close to half of 497 days. And 497 is ITs number of the beast.
The reason that 497 is a problem number is because of the use of a 32 bit counter to record uptime. If you record a tick for every 10 msec of uptime, then a 32-bit counter will overflow after approximately 497.1 days. This is because a 32 bit counter equates to 2^32, which can count 4,294,967,296 ticks. Because a tick is counted every 10 msec, we create 8,640,000 ticks per day (100*60*60*24). So after 497.102696 days, the counter will overflow. What happens next depends on good programming.
Some classic bugs can be foun
Now let me be clear: I am not aware of any active disruptive, brin