E: Alternative Ways to Assign an IP Address
XPress™ DR Industrial Device Server User Guide
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192.2.1.123
This is called decimal-dot notation.
The IP address is divided in two parts: network and host. To support different needs, three
network classes
have been defined. Depending on the network class, the last one, two or three
bytes define the host, while the remaining part defines the network. In the following explanations,
x
stands for the host part of the IP address:
Class A Network
IP address 1.x.x.x to 127.x.x.x
Only 127 different networks of this class exist. These have a very large number of potential
connected devices (up to 16,777,216).
Example: 10.0.0.1, (network 10, host 0.0.1)
Class B Network
IP address 128.0.x.x to 191.255.xxx.xxx
These networks are used for large company networks. Every network can consist of up to 65,534
devices.
Example: 172.1.3.2 (network 172.1, host 3.2)
Class C Network
IP address 192.0.0.xxx to 223.255.255.xxx
These network addresses are most common and are often used in small companies. These
networks can consist of a maximum number of 254 hosts.
Example: 192.7.1.9 (network 192.7.1, host 9)
The remaining addresses 224.x.x.x - 239.x.x.x are defined as ”class D” and are used as multicast
addresses.
The addresses 240.x.x.x. - 254.x.x.x are defined as class E and are reserved addresses.
Network Address
The host address with all host bits set to 0 is used to address the network as a whole (in routing
entries, for example).
Broadcast Address
The address with the host part bits set to 1 is the broadcast address, meaning for every station.
Network and broadcast addresses must not be used as a host address (for example, 192.168.0.0
identifies the entire network and 192.168.0.255 identifies the broadcast address).
IP Netmask
The netmask is used to divide the IP address differently from the standard defined by classes A,
B, C. A netmask defines how many bits from the IP address are to be taken as the network
section and how many bits are to be taken as the host section. When the number of host bits is
entered, the XPress DR calculates the netmask. The netmask is displayed in standard decimal-
dot notation.
