ZyXEL Communications PLA-470 V2 - V3.0.5 Installationsanleitung PDF herunterladen (Seite 232)

0000000 and 0111111 in the binary format. Knowing that addresses 0.0.0.0.

and 127.0.0.0 are reserved, there are therefore 2

– 2, i.e., 126 available class

A network addresses, ranging from 1.0.0.0 to 126.0.0.0.

The number of hosts is defined on 3 bytes (24 bits). Since the broadcast

address (x.x.x.255) and address x.x.x.0 are reserved, this gives 2

– 2, i.e.,

16,777,214 possible hosts per class A network address.

•

For class B addresses, the first 2 bytes (16 bits) are used to define the network

address with the first two bits set to 1 and 0. There are therefore 2

– 2, i.e.,

16,384 available class B network addresses, ranging from 128.0.0.0 to

191.255.0.0.

The number of hosts per network address is defined on 2 bytes. Like for

class A addresses, since the broadcast address and address x.x.x.0 are

reserved, there are therefore 2

– 2, i.e., 65,534 possible hosts per class B net-

work address.

•

For class C addresses, the first 3 bytes (24 bits) are used with the first three bits

set to 1.1 and 0, which gives 2

– 2, i.e., 2,097,152 available class C network

addresses, ranging from 192.0.0.0 to 223.255.255.0.

The number of hosts is defined on 1 byte (8 bits). Likewise, since the broad-

cast address and address x.x.x.0 are reserved, there are 2

– 2, i.e., 254 hosts

per class C network address.

Class C and D addresses are reserved for experimental multicast addressing.

IP addresses are not automatically allocated, and any address range cannot be

allocated to a network. The IANA (Internet Assigned Numbers Agency) is in charge

of giving these addresses to any requestor. However, notice that all the available

class A and B addresses are already allocated.

IP addresses are routable addresses. This means that they cannot be used for pri-

vate use.

To avoid improper IP addressing use, the IANA has reserved the three following

address ranges for the three main classes for strictly private use:

•

Class A: 10.0.0.1 to 10.255.255.254

•

Class B: 172.16.0.1 to 172.63.255.254

•

Class C: 192.168.0.0 to 192.168.255.254

To connect to a network with a different addressing plan or to the Internet, each

station having a private IP address must specify a default gateway address. This

address corresponds to a station dealing with network routing and is used both for

sending and receiving requests from a nonroutable environment (private network)

to a routable environment (Internet).

In the case of Internet connection sharing via a gateway, the gateway is in

charge of sending requests from a private (therefore nonroutable) environment to

the Internet (routable) environment. In this case, the default gateway address is the

gateway IP address.

Configuring Network Parameters 213

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ZyXEL Communications PLA-470 V2 - V3.0.5 Installationsanleitung Seite 232

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