What is the difference amoung a /24 a /27 and a /28 in DNS terms?

Question

Yes I know it's stupid question, but I can't find the answer in my O'Reilly DNS and Bind book or Yahoo.

Answer 1

just to add to the first answer, /24 means 24 binary positions used for subnet.



each segment of your IP address are representing binary bits.



lets say 192.168.1.20 =11000000.10100000.00000001.00010100



so in a subnet maskif it says 24 in bynary it looks like this:



11111111.11111111.11111111.00000000

which is:

255.255.255.0

the amount of 1´s is 24.



let´s look at 27:

11111111.11111111.11111111.11100000

which is:

255.255.255.224



I don´t know if you needed this info but I thought it might help you see that you don´t need it for DNS.

Answer 2

It has nothing to do with DNS. It has to do with Subnetting (the subnet mask setting) in your network settings.



The short answer is, all the computers in a network need to have the same subnet mask. The most common is 255.255.255.0 (which is also expressed as /24).



The link below has more info.

Answer 3

yep the one above answered it... it's subnetting, and what the ipaddress extents will legaly be allowed to have.