The value tFilterRSTLastType is 'ipAddress'. Although
this seems to be unfriendly for IPv6, we have to
recognize that there are a number of older MIBs that do
contain an IPv4 format address, known as IpAddress.
IPv6 addresses are represented using TAddress or InetAddress,
and so the underlying datatype is OCTET STRING, and their
value would be stored in the tFilterRSTLastOctetStringVal
column.