The value of vRtrPimNgAFGenCBSRHashMaskLen specifies the length of
a mask that is to be ANDed with the group address before
the hash function is called. All groups with the same hash
map to the same RP. For example, if this value is 24, only the first
24 bits of the group addresses matter. This mechanism is used to
map one group or multiple groups to a RP.
Default values are 30 and 126 for ipv4 and ipv6 group addresses
respectively.