Generally, if a parity error occurs only once, it is considered a soft parity error.
If a parity error occurs only once, monitor for another occurrence. At the first occurrence of a parity error, it is not possible to distinguish between a soft or hard parity error. Most parity error occurrences are soft parity errors and can usually be dismissed. If you have recently changed some hardware or have moved the box, try reseating the VIP. Frequent multiple parity error occurrences signify faulty hardware.
Soft parity errors are 10 to 100 times more frequent than hard parity errors. To greatly reduce the impact on your network, wait for a second parity error before replacing anything.