Dr. Mark Humphrys

School of Computing. Dublin City University.

Home      Blog      Teaching      Research      Contact

Search:

CA216      CA249      CA318

CA400      CA651      CA668


Network classes

The old way of handing out IP addresses.



Summary from here.





Example - DCU's block of addresses

DCU has the following block of addresses:
Dublin City University (NET-DCU-NET)
   Glasnevin
   Dublin, 9
   IE

   Netname: DCU-NET
   Netblock: 136.206.0.0 - 136.206.255.255
i.e. room for 2562 = 65,536 addresses.

DCU addresses run from:
136.206.0.0     to:
136.206.255.255
In binary, from:
1000 1000 1100 1110 0000 0000 0000 0000     to:
1000 1000 1100 1110 1111 1111 1111 1111
See IP decimal-binary table

First 16 bits are the DCU network number 136.206.
This is in binary:
1000 1000 1100 1110
Second 16 bits are the host number on that network.

This is a Class B network.
To be precise, the leading 10 indicates Class B, then the network number is the 14 bit:
00 1000 1100 1110
So a DCU address is:
Class B identifier, DCU network, machine number n:
10 00 1000 1100 1110 nnnn nnnn nnnn nnnn




IP address shows network class.


Special IP addresses.
See Reserved IP addresses and Private network.




Feeds      w2mind.org

On Internet since 1987.