This object specifies the size of the IP prefix cache
associated with this set of IP prefixes. The IP prefix cache
provides a list of IP prefixes most recently returned to this
range of IP prefixes. The IP address pool manager always
allocates IP prefixes from the IP prefix cache first.
If an implementation does not support address caching, then it
must report a value of zero for this object and it must not
allow write access to this object.