3Com CoreBuilder 3500, Руководство по внедрению

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264 C
HAPTER
11: I
NTERNET
P
ROTOCOL
(IP)
Network-Layer
Address
The network-layer address refers to a logical address that applies to a
specific protocol. A network-layer address exists at Layer 3 of the OSI
reference model.
IP Addresses IP addresses are 32-bit addresses that consist of a network part (the
address of the network where the host is located) and a host part (the
address of the host on that network). See Figure 42.
Figure 42 IP Address: Network Part and Host Part
IP addresses differ from Ethernet and Fiber Distributed Data Interface
(FDDI) MAC addresses, which are unique hardware-configured 48-bit
addresses. A central agency assigns the network part of the IP address,
and you assign the host part. All devices that are connected to the same
network share the same network part (also called the
prefix ).
Dotted Decimal Notation
The actual IP address is a 32-bit number that is stored in binary format.
These 32 bits are segmented into 4 groups of 8 bits — each group is
referred to as a
field
or an
octet
. Decimal notation converts the value of
each field into a decimal number, and the fields are separated by dots.
Figure 43
Dotted Decimal Notation for IP addresses
The decimal value of an octet whose bits are all 1s is 255.
IP Address
network host
32 bits
The boundary between network
and host parts depends on the
class of IP network.
158.101.10.32
10011110.01100101.00001010.00100000 = Binary notation
= Decimal notation