Unit installation

Installation and Operation Manual Appendix B SNMP Management
FCD-E1 IP Environment B-5
The network portion of an IP address can be one, two or three bytes long, in
accordance with the IP address class. This arrangement is illustrated below:
IP ADDRESS
Byte 1 Byte 2 Byte 3 Byte 4
Class A Network Portion Host Portion
Class B Network Portion Host Portion
Class C Network Portion Host Portion
The class of each IP address can be determined from its leftmost byte, in
accordance with the following chart:
Address Class First Byte Address Range
Class A 0 through 127 0.H.H.H through 127.H.H.H
Class B 128 through 191 128.N.H.H through 191.N.H.H
Class C 192 through 223 192.N.N.H through 223.N.N.H
N − indicates bytes that are part of the network portion
H − indicates bytes that are part of the host portion
• Host Portion − The host portion is used to identify an individual host
connected to the network. The host identifier is assigned by the using
organization, in accordance with its specific needs.
Often, the host portion is further sub-divided into two portions:
 Subnet number – For example, subnet numbers can be used to identify
departmental subnetworks. The subnet number follows the network
identifier.
 Host number – the last bits of the IP address.
The all-zero host identifier is always interpreted as a network identifier, and must
not be assigned to an actual host.
Net and Subnet Masks
Net and subnet masks are used to help filter the relevant traffic more efficiently:
the function of the net and subnet mask is to specify how many of the IP address
bits are actually used for the net identifier and for the subnet number.
The mask is a 32-bit word that includes “ones” in the positions used for net and
subnet identifications, followed by “zeros” up to the end of the IP address. For
example, the subnet mask corresponding to the Class C IP address 194.227.31.67
is 255.255.255.000.
Not
e