HP 620n User's Guide download pdf (Page 241)

ENWW TCP/IP Overview 241

Subnets

When an IP network address for a particular network class is

assigned to an organization, no provision is made for more than

one network being present at that location. Local network

administrators use subnets to partition a network into several

different subnetworks. Splitting a network into subnets can result

in better performance and improved use of limited network

address space.

Subnet Mask

The subnet mask is a mechanism used to divide a single IP network

into several different subnetworks. For a given network class, a

portion of an IP address that would normally be used to identify a

node is used, instead, to identify a subnetwork. A subnet mask

is applied to each IP address to specify the portion used for

subnetworks, and the portion used to identify the node.

For example, see Table A.3

As illustrated in Table A.3

, the Class A IP network address “15”

has been assigned to company ABC. To allow additional networks

at company ABC’s site, the subnet mask of 255.255.0.0 is used. This

subnet mask specifies that the second byte of the IP address will be

used to identify up to 254 subnets. Using this designation, each

device is uniquely identified on its own subnet, but company ABC

can incorporate up to 254 subnetworks without violating their

assigned address space.

Table A.3 Example: Subnet Mask 255.255.0.0 Applied to Class A

Network

Class A Network Address 15 xxx xxx xxx

Subnet Mask 255 255 0 0

IP Address fields with Subnet

Mask applied

Network

Subnet Host Host

Example of a node’s IP Address

on Subnet 1

1 25 7

Example of a node’s IP Address

on Subnet 254

254 64 2

1 2 ... 236 237 238 239 240 241 242 243 244 245 246 ... 263 264

No comments

HP 620n User's Guide Page 241