Structure Of An Ipv4 Address - Siemens SCALANCE XM-400 Configuration Manual

2.6.4

Structure of an IPv4 address

Address classes
IPv4 address range
1.x.x.x to 126.x.x.x
128.0.x.x to
191.255.x.x
192.0.0.x to
223.255.255.x
224.0.0.0 -
239.255.255.255
240.0.0.0 -
255.255.255.255
IPv4 address format - notation
An IPv4 address consists of 4 bytes. Each byte is represented in decimal, with a dot
separating it from the previous one.
XXX.XXX.XXX.XXX
XXX stands for a number between 0 and 255
The IPv4 address consists of two parts:
● The address of the (sub) network
● The address of the node (generally also called end node, host or network node)
Subnet mask
The subnet mask separates these two addresses. It decides which part of the IPv4 address
addresses the network and which part of the IPv4 address addresses the node.
The set bits in the subnet mask decide the network part of the IPv4 address.
Example:
IPv4 address: 140.80.0.2
Subnet mask: 255.255.0.0 = 11111111.11111111.00000000.00000000
The first 2 bytes of the IPv4 address decide the subnet - therefore 140.80. The last two bytes
address the node - therefore 0.2.
The following applies in general:
● The network address is obtained from ANDing the IPv4 address and subnet mask.
● The node address is obtained from AND NOT logic operation on the IPv4 address and
subnet mask.
Outside the local area network, the distinction between network ID and host ID is of no
significance, in this case packets are delivered based on the entire IPv4 address.
SCALANCE XM-400/XR-500 Command Line Interface (CLI)
Configuration Manual, 11/2015, C79000-G8976-C252-10
Max. number of Max. number of
networks hosts/network
126
16383
2097151
Multicast applications
Reserved for future applications
2.6 Interface identifiers and addresses
Class
16777214 A
65534 B
254 C
D
E
Description
CIDR
/8
/16
/24
45