A table of mappings from network layer address to physical
address to interface.
The probe will add entries to this table based on the source
MAC and network addresses seen in packets without MAC-level
errors. The probe will populate this table for all protocols
in the protocol directory table whose value of
protocolDirAddressMapConfig is equal to supportedOn(3), and
will delete any entries whose protocolDirEntry is deleted or
has a protocolDirAddressMapConfig value of supportedOff(2).