Sun Microsystems StorageTek StreamLine SL8500, System Assurance Manual

Page: 211 / 278

E24254-01 Appendix G TCP/IP Connectivity 189
TCP/IP Connectivity
■
Subnet Masks
Definitions:
• Subnets allow network administrators to further divide the host part of an
IP address into further, smaller, networks—subnets.
• A mask is a filter that selectively includes or excludes certain values.
Values that do not conform to the mask can not access the device.
• A subnet mask , or netmask , is a 32-bit mask that divides an IP address
into subnets and specifies the available hosts on a network.
A subnet mask looks like an IP address and is often seen in 255.255.255.0
notation. It uses a “1” bit to filter, or “mask” allowable addresses in the
network.
For example: 255.255.255.0 is a subnet mask.

Where:
- 255 values mask the access of an IP address range and
- 0 (or 000) values allow the access of an IP address range
When configuring the IP address, including the “slash” notation (for example /
24) is known as Classless Inter-Domain Routing (CIDR
1
) format and indicates
the subnet mask for that IP address. While the more conventional notation
255.255.255.0 provides the same information, the subnet mask is more
concise using the CIDR notation.
Here is an example of a netmask, binary conversion, and the number of bits
masked.
The above example is a 32-bit address, which is a broadcast address and
does not allow any hosts, computers, or other network devices access.
1. CIDR is often pronounced as Cedar.
Netmask First Octet Second Octet Third Octet Fourth Octet
255. 255. 255. 255
Conversion 11111111 11111111 11111111 11111111
Netmask length

(CIDR notation)
/8 /16 /24 /32