Apple Mac OS X Server (Administrator’s Guide) - Manual (Page 528)

528 Chapter 15
The segments in a mask go from general to specific, so the earlier a zero appears in the
segments of the subnet mask, the wider the resulting range of addresses. A subnet mask of
255.255.255.255 is the narrowest and indicates a single IP address.
Any value except 255 in a segment of the subnet mask must be followed by zero segments.
The following subnet mask examples are invalid, because in each case, a value other than 255
is followed by a non-zero value:
m 255.255.128.255
m 255.0.128.128
m 255.255.252.255
Using Address Ranges
When you create filters using Server Settings, you enter an IP address and a subnet mask.
Server Settings shows you the resulting address range, and you can change the range by
modifying the subnet mask. When you indicate a range of possible values for any segment of
an address, that segment is called a wildcard. The following below gives examples of address
ranges created to achieve specific goals.
Goal
Sample
IP address
Subnet mask Address range
Create a filter that specifies a
single IP address. 10.221.41.33 255.255.255.255 10.221.41.33
(single address)
Create a filter that leaves the
last segment of the IP address
range as a wildcard. 10.221.41.33 255.255.255.0 10.221.41.0 to
10.221.41.255
Create a filter that leaves part of
the third segment and all of the
fourth segment as a wildcard. 10.221.41.33 255.255.252.0 10.221.40.0 to
10.221.43.255
Create a filter that applies to all
incoming addresses. Select “All IP
addresses” All IP addresses