Proxicast LAN-Cell 2 User's Guide download pdf (Page 606)

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Appendix C IP Addresses and Subnetting

LAN-Cell 2 User’s Guide

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An IP address with host IDs of all zeros is the IP address of the network (192.168.1.0 for

example). An IP address with host IDs of all ones is the broadcast address for that network

(192.168.1.255 for example). Therefore, to determine the total number of hosts allowed in a

network, deduct two as shown next:

• A class C address (1 host octet: 8 host bits) can have 2

– 2, or 254 hosts.

• A class B address (2 host octets: 16 host bits) can have 2

– 2, or 65534 hosts.

A class A address (3 host octets: 24 host bits) can have 2

– 2 hosts, or approximately 16

million hosts.

IP Address Classes and Network ID

The value of the first octet of an IP address determines the class of an IP address as already

stated. These are the details of how that range is determined.

• Class A addresses have a 0 in the leftmost bit.

• Class B addresses have a 1 in the leftmost bit and a 0 in the next leftmost bit.

• Class C addresses start with 1 1 0 in the first three leftmost bits.

• Class D addresses begin with 1 1 1 0. Class D addresses are used for multicasting, which is

used to send information to groups of computers.

• There is also a class E. It is reserved for future use.

The following table shows the allowed ranges for the first octet of each class. This range

determines the number of subnets you can have in a network.

Subnet Masks

A subnet mask is used to determine which bits are part of the network number, and which bits

are part of the host ID (using a logical AND operation).

A subnet mask has 32 bits. If a bit in the subnet mask is a “1” then the corresponding bit in the

IP address is part of the network number. If a bit in the subnet mask is “0” then the

corresponding bit in the IP address is part of the host ID.

Class B Network number Network number Host ID Host ID

Class C Network number Network number Network number Host ID

Table 239 Allowed IP Address Range By Class

CLASS ALLOWED RANGE OF FIRST OCTET (BINARY)

ALLOWED RANGE OF FIRST

OCTET (DECIMAL)

Class A 00000000 to 01111111 0 to 127

Class B 10000000 to 10111111 128 to 191

Class C 11000000 to 11011111 192 to 223

Class D 11100000 to 11101111 224 to 239

Class E

(reserved)

11110000 to 11111111 240 to 255

Table 238 Classes of IP Addresses (continued)

IP ADDRESS OCTET 1 OCTET 2 OCTET 3 OCTET 4

1 2 ... 601 602 603 604 605 606 607 608 609 610 611 ... 649 650

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