IP Subnet


An IP address consists of four parts divided by dots. Each part can have a value from 0 to 255. For example a valid IP address could be Usually the first two or three bytes represent the network of say an office, here 172.13.14 and the range from 0 to 255 that identifies each host. Now, if a PC wants to access another one using the IP protocol, there has to be an information, whether the LAN is split up or not, that means if subnets are used. For this reason too, there is an additional information, called the netmask.
If you got the netmask, then the PC would know (or better his IP stack), that the leading three parts of his ip adress belong to his own lan and that the different machines are enumerated with the last bye. To find out, how many workstations are belonging to this network, just calculate 256-0 equals 256. So, the network isn't divided up into subnets, all 256 possible adresses can be found in this lan.
Now consider this netmask: That means there are 256-192=64 hosts on this network. We got four different subnets, the first one with hosts from, the second one form, the third one and the last one
If the PC has got the IP address with the netmask, then it would belong to the range of subnet #2.
The first address of the network, in this example the 172.13.14.[0;64;128;192] cannot be used as an host ip address, cause this is the ip adress of the network itself. Also don't use the last ip address, cause this is used for broadcasts on the lan (172.13.14.[63;127;191;255])

Wichtige Links

IP Netze und Subnetze (TLK)
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