Avaya Configuring IP, ARP, RARP, RIP, and OSPF Services Instrukcja Użytkownika Pobierz pdf (Strona 24)

Configuring IP, ARP, RARP, RIP, and OSPF Services

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308627-14.20 Rev 00

IP Addresses

An IP address consists of 32 bits that have the form network.host. The network

portion is a network number ranging from 8 to 24 bits. The host portion is the

remaining 8 to 24 bits identifying a specific host on the network. The Internet

Network Information Center (NIC) assigns the network portion of the IP address.

Your network administrator assigns the host portion.

NIC recognizes three primary classes of networks: A, B, and C. In addition, NIC

has recently identified two other classes: Class D for networks that support

multicasting, which allows an IP datagram to be transmitted to a single multicast

group consisting of hosts spread across separate physical networks; and Class E

for experimental networks. The IP router does not fully support Class D or Class E

networks.

Based on the size of the network, NIC classifies a network as Class A, B, or C (the

most common). The network class determines the number of bits assigned to the

network and host portions of the IP address (Table 1-1

The position of the first bit set to 0 (whether it is the first, second, third, or fourth

bit) in the first octet of an IP address indicates the network class (A, B, C, or D). If

no bit is set to 0, it is a Class E network. Figure 1-1

shows the placement of the

first bit set to 0 for Class A, B, and C networks. The figure also shows how a

network’s class affects the network and host portions of the IP address.

Table 1-1. Network Classes and IP Addresses

Network Size Class Network Portion Host Portion

More than 65,533 hosts A 8 bits 24 bits

254 to 65,533 hosts B 16 bits 16 bits

Fewer than 254 hosts C 24 bits 8 bits

1 2 ... 19 20 21 22 23 24 25 26 27 28 29 ... 389 390

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Avaya Configuring IP, ARP, RARP, RIP, and OSPF Services Instrukcja Użytkownika Strona 24