use NetAddr::IP;
__PACKAGE__->has_a( ip_addr => 'NetAddr::IP' 
    inflate => sub { 
        my $packed = shift;
        # Unpack the IP addr here into $ip and $netmask
        return NetAddr::IP->new( $ip, $netmask );
    }, 
    deflate => sub { 
        my $addr = shift;
        # Take the NetAddr::IP instance and pack it 
        # into $packed
        return $packed;
    }, 
);