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Key Concepts
265
Network Portion
The location of the boundary between the network part and the host
part depends on the class that the central agency assigns to your
network. The three primary classes of IP addresses are A, B, and C:
■
Class A address
— Uses 8 bits for the network part and 24 bits for
the host part. Although only a few Class A networks can be created,
each can contain a very large number of hosts.
■
Class B address
— Uses 16 bits for the network part and 16 bits for
the host part.
■
Class C address
— Uses 24 bits for the network part and 8 bits for
the host part. Each Class C network can contain only 254 hosts, but
many such networks can be created.
The high-order bits of the network part of the address designate the IP
network class. See Table 38.
Subnet Portion
The IP address can also contain a
subnet part
at the beginning of the host
part of the IP address. Thus, you can divide a single Class A, B, or C
network internally, allowing the network to appear as a single network to
other external networks. The subnet part of the IP address is visible only
to hosts and gateways on the subnet.
When an IP address contains a subnet part, a
subnet mask
identifies the
bits that constitute the subnet address and the bits that constitute the
host address. A subnet mask is a 32-bit number in the IP address format.
The
1
bits in the subnet mask indicate the network and subnet part of the
address. The
0
bits in the subnet mask indicate the host part of the IP
address, as shown in Figure 44.
Table 38
How Address Class Corresponds to the Address Number
Address Class
High-order Bits
Address Number
(Decimal)
A
0nnnnnnn
0-127
B
10nnnnnn
128-191
C
11nnnnnn
192-254
Summary of Contents for CoreBuilder 3500
Page 44: ...44 CHAPTER 2 MANAGEMENT ACCESS ...
Page 58: ...58 CHAPTER 3 SYSTEM PARAMETERS ...
Page 86: ...86 CHAPTER 5 ETHERNET ...
Page 112: ...112 CHAPTER 6 FIBER DISTRIBUTED DATA INTERFACE FDDI ...
Page 208: ...208 CHAPTER 9 VIRTUAL LANS ...
Page 256: ...256 CHAPTER 10 PACKET FILTERING ...
Page 330: ...330 CHAPTER 12 VIRTUAL ROUTER REDUNDANCY PROTOCOL VRRP ...
Page 356: ...356 CHAPTER 13 IP MULTICAST ROUTING ...
Page 418: ...418 CHAPTER 14 OPEN SHORTEST PATH FIRST OSPF ...
Page 519: ...RSVP 519 Figure 94 Sample RSVP Configuration Source station End stations Routers ...
Page 566: ...566 CHAPTER 18 DEVICE MONITORING ...
Page 572: ...572 APPENDIX A TECHNICAL SUPPORT ...
Page 592: ...592 INDEX ...