If the sensor is configured and working correctly then the shun should have
been removed from the PIX after it timed out. The most common reason
for a shun to remain on a blocking device after it times out on the sensor
is if communications with the blocking device has been lost. To check
this in IDM, click Monitoring/Statistics. Search for NetworkAccess Statistics.
The PIX device should be listed, and the state should be Active. If
not, then something is wrong with the sensor configuration for the PIX,
or possibly with network connectivity between sensor and PIX.
On the PIX, there is no difference between a host shun and a connection
shun. In either case, all packets from the attacking host are dropped
unconditionally.