Solved

class B subnetting

Posted on 2007-11-17
8
589 Views
Last Modified: 2008-02-01
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) ?
Jim
0
Comment
Question by:dimi67
  • 3
  • 3
  • 2
8 Comments
 
LVL 1

Expert Comment

by:beckman55
ID: 20304926
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

x.y.0.0
x.y.16.0
x.y.32.0
x.y.48.0
etc

x.y.0.1-x.y.15.254

x.y.16.1-etc

I hope that answers your question.  If not please give me some more information
0
 
LVL 5

Accepted Solution

by:
pavaneeshkumar earned 500 total points
ID: 20304984
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

255.255.0.0 	1—standard subnet mask		65,534

255.255.128.0 	Invalid—only 1 bit for subnet portion

255.255.192.0 	2 				16,382

255.255.224.0 	6 				8,190

255.255.240.0 	14 				4,094

255.255.248.0 	30 				2,046

255.255.252.0 	62 				1,022

255.255.254.0 	126 				510

255.255.255.0 	254 				254

255.255.255.128 510 				126

255.255.255.192 1,022 				62

255.255.255.224 2,046 				30

255.255.255.240 4,094 				14

255.255.255.248 8,190 				6

255.255.255.252 16,382 				2

255.255.255.254 Invalid—only 1 bit left for host portion 

255.255.255.255 Invalid—no bits left for host portion

Open in new window

0
 

Author Comment

by:dimi67
ID: 20305010
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...
0
 
LVL 1

Expert Comment

by:beckman55
ID: 20305027
valid subnets can only end in the following 0,128,192,224,240,248,252,254,255

So 255.255.0.0 and 255.255.240.0 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 255.255.240.0 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
0
6 Surprising Benefits of Threat Intelligence

All sorts of threat intelligence is available on the web. Intelligence you can learn from, and use to anticipate and prepare for future attacks.

 
LVL 1

Expert Comment

by:beckman55
ID: 20305034
maybe just a little more to clarify:

IP address example:  

10.10.16.1 - ip
255.255.240.0 - subnet

10.10.32.1.
255.255.240.0
0
 

Author Comment

by:dimi67
ID: 20305162
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?
thanks
0
 
LVL 5

Expert Comment

by:pavaneeshkumar
ID: 20305232
255.255.26.0 is an invalid subnet
and
255.255.240.0 is a valid sunbet for class B.

please have a look on the table posted previously.
0
 
LVL 5

Expert Comment

by:pavaneeshkumar
ID: 20305237
also there are only 14 valid subnet under Class B network not 16.
0

Featured Post

How your wiki can always stay up-to-date

Quip doubles as a “living” wiki and a project management tool that evolves with your organization. As you finish projects in Quip, the work remains, easily accessible to all team members, new and old.
- Increase transparency
- Onboard new hires faster
- Access from mobile/offline

Join & Write a Comment

In the world of WAN, QoS is a pretty important topic for most, if not all, networks. Some WAN technologies have QoS mechanisms built in, but others, such as some L2 WAN's, don't have QoS control in the provider cloud.
Load balancing is the method of dividing the total amount of work performed by one computer between two or more computers. Its aim is to get more work done in the same amount of time, ensuring that all the users get served faster.
After creating this article (http://www.experts-exchange.com/articles/23699/Setup-Mikrotik-routers-with-OSPF.html), I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…
After creating this article (http://www.experts-exchange.com/articles/23699/Setup-Mikrotik-routers-with-OSPF.html), I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…

759 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

21 Experts available now in Live!

Get 1:1 Help Now