class B subnetting

If we have a class B network x.y.0.0/20 for example.
How many subnets we have ? 16 or 14?
That means x.y.0.0 and x.y.240.0 are valid subnets or must be reserved to notify the hole
net(x.y.0.0) and  broadcast to all subnets (x.y.240.0) ?
Who is Participating?

[Product update] Infrastructure Analysis Tool is now available with Business Accounts.Learn More

I wear a lot of hats...

"The solutions and answers provided on Experts Exchange have been extremely helpful to me over the last few years. I wear a lot of hats - Developer, Database Administrator, Help Desk, etc., so I know a lot of things but not a lot about one thing. Experts Exchange gives me answers from people who do know a lot about one thing, in a easy to use platform." -Todd S.

With the subnet you have you have an incrementing factor of 16.   So your ip address' will be as follows:  with a subnet mask of /20




I hope that answers your question.  If not please give me some more information
The table below summarizes all of the Class B subnet masks and the number of
networks and hosts.
Subnet Mask 	# of Unique Valid Networks	# of Hosts on Each Network 	1—standard subnet mask		65,534 	Invalid—only 1 bit for subnet portion 	2 				16,382 	6 				8,190 	14 				4,094 	30 				2,046 	62 				1,022 	126 				510 	254 				254 510 				126 1,022 				62 2,046 				30 4,094 				14 8,190 				6 16,382 				2 Invalid—only 1 bit left for host portion Invalid—no bits left for host portion

Open in new window


Experts Exchange Solution brought to you by

Your issues matter to us.

Facing a tech roadblock? Get the help and guidance you need from experienced professionals who care. Ask your question anytime, anywhere, with no hassle.

Start your 7-day free trial
dimi67Author Commented:
the two answers are different...wich is the correct?? 14 or 16??
kumar please be more specific..why x.y.0.0 and x.y.240.0 are not valid subnets?
Thanks in advance...
CompTIA Network+

Prepare for the CompTIA Network+ exam by learning how to troubleshoot, configure, and manage both wired and wireless networks.

valid subnets can only end in the following 0,128,192,224,240,248,252,254,255

So and are both valid subnets.  It depends on how your networking them and how you want to use them.  His chart is correct you will only get 14 networks with a subnet.    My half that I explained shows how those 14 networks are broken up in the x.y.240.0 subnet.  x.y.0.0,x.y.16.0, 32, 48, 64, etc 14 times till you max that subnet.

Give us a little more info on what your trying to accomplish if that doesn't answer your question
maybe just a little more to clarify:

IP address example: - ip - subnet
dimi67Author Commented:
in the sequence of x.y.0.0, x.y.16.0 ...x.y.240.0 we have 16 subnets and not 14...the question is : is 16.0 and 240.0 valid subnets?
pavaneeshkumarCommented: is an invalid subnet
and is a valid sunbet for class B.

please have a look on the table posted previously.
also there are only 14 valid subnet under Class B network not 16.
It's more than this solution.Get answers and train to solve all your tech problems - anytime, anywhere.Try it for free Edge Out The Competitionfor your dream job with proven skills and certifications.Get started today Stand Outas the employee with proven skills.Start learning today for free Move Your Career Forwardwith certification training in the latest technologies.Start your trial today
Network Architecture

From novice to tech pro — start learning today.