IP addressing

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Hi,
I'm studying for the 291 exam, and going over IP address classes. I think i have it.

But at my place of work the address range we use is 10.128.72.1 - 10.128.73.254 with 255.255.254.0. Should we not be using Class C addressing?

or am i missing something?

 

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You're missing something.

Just because an IP address range is a certain class doesn't mean that you have to use a certain subnet mask.

By using a different class of subnet mask you merely restrict the amount of available host IP addresses on the subnet.

This recent thread may help you.

If you have any specific questions then PM me.

Qs

 

The private IP addresses defined are as follows:
● Class A private IP addresses 10.0.0.0 through 10.255.255.255
● Class B private IP addresses 172.16.0.0 through 172.31.255.255
● Class C private IP addresses 192.168.0.0 through 192.168.255.255

The above is for the text book. the reason i say we should have class C is because of the number of addresses we require. would it not be better practice to have used 192.168. address?

 

The text-book is just trying to keep it simple. In the real world you can specify different masks to restrict the amount of IP addresses on a subnet.

...If you want me to be really vague, but pretty honest - you don't need to worry about it for your exam. Just stay in the blissful ignorance that Class A IP addresses only have a Class A subnet mask etc etc etc

Else, PM me and I'll explain further if you're curious.

Qs

 

They could be using the range for future proofing for expansion, or they may have multiple subnets that perhaps you are not aware of.

Or it could be they just like the number 10 alot

 

cheers guys. any links or books anyone can recommend to help me get a better grip on this area.

 

TRY THIS

If you goodle VLSM you will find a ton of information out there.

 

Sorry dude, work went a bit crazy.

Here's a guide to VLSM (variable length subnet masking) - http://www.tcpipguide.com/free/t_IPVariableLengthSubnetMaskingVLSM.htm

Qs

 

...but, but that's CCNA stuff and CCNA qualified people are eeeevil.

 

cheers guys i'll take a look when work calms down abit.

 

O deffo srsly!

 

You missing the distinction between classful and classless.

http://www.infocellar.com/networks/ip/classful-vs-classless.htm

The rules you're using are old and really no longer apply, everyone has gone classless.

 

thanks

 

yarly!