Netgear NTGWGR614 User Manual download pdf (Page 91)

Reference Manual for Cable/DSL Wireless Router WGR614

Network, Routing, Firewall, and Basics B-5

As a shorter alternative to dotted-decimal notation, the netmask may also be expressed in terms of

the number of ones from the left. This number is appended to the IP address, following a backward

slash (/), as “/n.” In the example, the address could be written as 192.168.170.237/24, indicating

that the netmask is 24 ones followed by 8 zeros.

Subnet Addressing

By looking at the addressing structures, you can see that even with a Class C address, there are a

large number of hosts per network. Such a structure is an inefficient use of addresses if each end of

a routed link requires a different network number. It is unlikely that the smaller office LANs would

have that many devices. You can resolve this problem by using a technique known as subnet

addressing.

Subnet addressing allows us to split one IP network address into smaller multiple physical

networks known as subnetworks. Some of the node numbers are used as a subnet number instead.

A Class B address gives us 16 bits of node numbers translating to 64,000 nodes. Most

organizations do not use 64,000 nodes, so there are free bits that can be reassigned. Subnet

addressing makes use of those bits that are free, as shown below.

Figure 7-2: Example of Subnetting a Class B Address

A Class B address can be effectively translated into multiple Class C addresses. For example, the

address of 172.16.0.0 is assigned, but node addresses are limited to 255 maximum, allowing

eight extra bits to use as a subnet address. The IP address of 172.16.97.235 would be interpreted as

network address 172.16, subnet number 97, and node number 235. In addition to extending

the

number of addresses available, subnet addressing provides other benefits. Subnet addressing

allows a network manager to construct an address scheme for the network by using different

subnets for other geographical locations in the network or for other departments in the

organization.

7262

lass B

Network Subnet Node

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Netgear NTGWGR614 User Manual Page 91