This DisplayString is the network mask of the route to
which this policy applies. The following formats can be used:
IP cccc - ipAddress MIB
IP nnn.nnn.nnn.nnn - decimal dotted format
The agent will be smart enough to understand either one of
the two formats listed, based on the size of the argument given.
When performing an snmp get, the agent will unconditionally
return this value using the decimal dotted format.
a3ComRoutePolicyRouteMask will be ignored if the protocol family
is not ip or if a3ComRoutePolicyRouteAddress is empty. On the other
hand, an error will be returned if an invalid mask is existent
upon entry activation. The value of this object can be modified
at any time.