B: Network Configuration Using UDP
XPress™ DR Industrial Device Server User Guide
82
In most network examples, the host portion of the address is set to zero.
Table B-14 Available IP Addresses
Class
Reserved
Available
A
0.0.0.0
127.0.0.0
1.0.0.0 to 126.0.0.0
B
128.0.0.0
191.255.0.0
128.1.0.0 to 191.254.0.0
C
192.0.0.0
223.255.255.0
192.0.1.0 to
223.255.254.0
D, E
224.0.0.0 to 255.255.255.254
255.255.255.255
None
Consider the IP address 36.1.3.4. This address is a Class A address; therefore, the network
portion of the address is 36.0.0.0 and the host portion is 1.3.4.
Subnet Portion
The subnet portion of the IP address represents which
sub-network
the address is from. Sub-
networks are formed when an IP network is broken down into smaller networks using a
subnet
mask
.
A router is required between all networks and all sub-networks. Generally, hosts can send
packets directly only to hosts on their own sub-network. All packets destined for other subnets are
sent to a router on the local network.
Host Portion
The host portion of the IP address is a unique number assigned to identify the host.
Network Address
A host address with all host bits set to 0 addresses the network as a whole (for example, in
routing entries).
192.168.0.0
Broadcast Address
A host address with all host bits set to 1 is the broadcast address, meaning for “for every station.”
192.168.0.255
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 Subnet Mask
An IP subnet mask divides IP address differently than the standards defined by the classes A, B,
and C. An IP subnet mask defines the number of bits to be taken from the IP address as the
network or host sections. The device server prompts for the number of host bits to be entered and
then calculates the netmask, which is displayed in standard decimal-dot notation (for example,
255.255.255.0) when saved parameters are displayed.