IP Subnet
- This FAQ gives information about ip
subnets. How to use netmask and to calculate the number
of hosts and the first and last ip adress of a
subnet/net.
- It's useful if you need to configure a wan
connection to a subnetted ip lan.
- 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 172.13.14.32. 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
255.255.255.0, 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:
255.255.255.192. That means there are 256-192=64
hosts on this network. We got four different
subnets, the first one with hosts from
172.13.14.0-172.13.14.63, the second one form
172.13.14.64-172.13.14.127, the third one
172.13.14.128-172.13.14.191 and the last one
172.13.14.192-172.13.14.255.
- If the PC has got the IP
address 172.13.14.99 with the netmask
255.255.255.192, 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])
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Wichtige Links
- FAQ-Indexseite
IP Netze und Subnetze
(TLK)
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- If you have comments or
suggestions, send email at support@BinTec.DE