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ru.networks
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From : Dmitry Tcvetcov 2:5004/84 15 May 2002 21:18:02
To : Evgeniy_Lyulin
Subject : Классификация сетей
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EL> 1. Как классифицируются сети?
A: 1.0.0.0 - 126.255.255.255
Сети такого класса принадлежат правительству и самым крупным
корпорациям(IBM, HP...) данный момент уже не выдаются.
Кол-во возможных хостов - 2^24-2
B: 128.0.0.0 - 191.255.255.255
Для организаций поменьше, кол-во хостов 2^16-2
C: 192.0.0.0 - 223.255.255.255
Кол-во хостов, соотвессно: 2^8-2
Сети такого класса имеют, например, гос. университеты, провайдеры, и т.д.
Это я тебе очень вкрадце изложил нижеследующий материал, если есть
действительно жажда знаний - советую прочитать,
это из cisco networking academy program.
There are three classes of IP addresses that an organization can receive from
the American Registry for Internet Numbers (ARIN) (or the organization's ISP).
They are Class A, B, and C. ARIN now reserves Class A addresses for governments
throughout the world (although a few large companies, such as Hewlett Packard,
have received one in the past) and Class B addresses for medium-sized companies.
All other requestors are issued Class C addresses.
Class A
When written in a binary format, the first (leftmost) bit of a Class A address
is always 0. An example of a Class A IP address is 124.95.44.15. The first
octet, 124, identifies the network number assigned by ARIN. The internal
administrators of the network assign the remaining 24 bits. An easy way to
recognize whether a device is part of a Class A network is to look at the first
octet of its IP address, which will range from 0-126. (127 does start with a 0
bit, but has been reserved for special purposes.)
All Class A IP addresses use only the first 8 bits to identify the network part
of the address. The remaining three octets can be used for the host portion of
the address. Every network that uses a Class A IP address can have assigned up
to 2 to-the-power of 24 (224) (minus 2), or 16,777,214, possible IP addresses to
devices that are attached to its network.
Class B
The first 2 bits of a Class B address are always 10 (one and zero). An example
of a Class B IP address is 151.10.13.28. The first two octets identify the
network number assigned by ARIN. The internal administrators of the network
assign the remaining 16 bits. An easy way to recognize whether a device is part
of a Class B network is to look at the first octet of its IP address. Class B IP
addresses always have values ranging from 128 to 191 in their first octet.
All Class B IP addresses use the first 16 bits to identify the network part of
the address. The two remaining octets of the IP address can be used for the host
portion of the address. Every network that uses a Class B IP address can have
assigned up to 2 to-the-power of 16 (216) (minus 2 again!), or 65,534, possible
IP addresses to devices that are attached to its network.
Class C
The first 3 bits of a Class C address are always 110 (one, one and zero). An
example of a Class C IP address is 201.110.213.28. The first three octets
identify the network number assigned by ARIN. The internal administrators of the
network assign the remaining 8 bits . An easy way to recognize whether a device
is part of a Class C network is to look at the first octet of its IP address.
Class C IP addresses always have values ranging from 192 to 223 in their first
octet.
All Class C IP addresses use the first 24 bits to identify the network part of
the address. Only the last octet of a Class C IP address can be used for the
host portion of the address. Every network that uses a Class C IP address can
have assigned up to 28 (minus 2), or 254, possible IP addresses to devices that
are attached to its network.
С уважением, Dmitry Tcvetcov.
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* Origin: -= Abbey Road =- (2:5004/84)
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