Solved

Subnetting_why are these two subnets talking?

Posted on 2007-11-19
10
301 Views
Last Modified: 2012-06-21
Hi.  I expanded my (single - unrouted) network over the weekend by changing the subnet from 255.255.255.0 to 255.255.240.0.  I am fairly new to networking but thought that these were two separate subnets and so would not easily talk to each other.  I'm glad they do as my job was that much easier but why, during the changeover, did devices on each subnet still communicate with each other?  Will I lose connectivity at some point if I missed a subnet change on one of my devices.
0
Comment
Question by:valmatic
  • 3
  • 3
  • 2
  • +1
10 Comments
 
LVL 6

Accepted Solution

by:
MorDrakka earned 25 total points
ID: 20313059
Hi,

I think that is the case because the fact the two subnets overlap eachother if you have the same starting IPadress.

Let me explain:

Say at first you have this:

http://jodies.de/ipcalc?host=10.0.0.1&mask1=24&mask2=

And you are migrating to this:

http://jodies.de/ipcalc?host=10.0.0.1&mask1=20&mask2=

If you compare the 2 start hostname's with eachother you see they overlap eachother.

Does this clarify somewhat ?

M


0
 
LVL 7

Author Comment

by:valmatic
ID: 20313307
I understand what you mean about the overlap and that looks like exactly what's happening but I'm still unclear as to why that occurs.  (?)  
0
 
LVL 18

Assisted Solution

by:Johnjces
Johnjces earned 25 total points
ID: 20313478
That is the purpose of subnetting. You can easily allow several sub-networks to talk.

Get an IP calculator. That will show you easily the allowed ranges that can be created using a different IP subnet mask.

Here is a link for an online one:

http://jodies.de/ipcalc

Here is a free one from 3Com:

ftp://ftp.3com.com/pub/utilbin/win32/3CIPCalc.zip

Might help

John
0
What is SQL Server and how does it work?

The purpose of this paper is to provide you background on SQL Server. It’s your self-study guide for learning fundamentals. It includes both the history of SQL and its technical basics. Concepts and definitions will form the solid foundation of your future DBA expertise.

 
LVL 7

Author Comment

by:valmatic
ID: 20313508
THanks guys,  Guess that answers my question. :)
0
 
LVL 6

Expert Comment

by:MorDrakka
ID: 20314151
WHAT ? I believe I answered it. Johnices even gives the same link as I do.
0
 
LVL 18

Expert Comment

by:Johnjces
ID: 20314196
MorDrakka

I am so sorry! I did not read your post or I would have not included the online IP Calculator.

The only difference was a direct answer to his question, "...but why, during the changeover, did devices on each subnet still communicate with each other? " with; "That is the purpose of subnetting. You can easily allow several sub-networks to talk."

John
0
 
LVL 77

Expert Comment

by:Rob Williams
ID: 20314674
As an "innocent bystander", I would say MorDrakka deserves a point split as a minimum. If you like you can ask the moderators to re-evaluate in the community support forum.
http://www.experts-exchange.com/Community_Support/General/#browseZones
--Rob
0
 
LVL 18

Expert Comment

by:Johnjces
ID: 20315046
valmatic

I do concur with RobWill!

John
0
 
LVL 7

Author Comment

by:valmatic
ID: 20320252
points split.  
0

Featured Post

Netscaler Common Configuration How To guides

If you use NetScaler you will want to see these guides. The NetScaler How To Guides show administrators how to get NetScaler up and configured by providing instructions for common scenarios and some not so common ones.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Even if you have implemented a Mobile Device Management solution company wide, it is a good idea to make sure you are taking into account all of the major risks to your electronic protected health information (ePHI).
If you're not part of the solution, you're part of the problem.   Tips on how to secure IoT devices, even the dumbest ones, so they can't be used as part of a DDoS botnet.  Use PRTG Network Monitor as one of the building blocks, to detect unusual…
Viewers will learn how to connect to a wireless network using the network security key. They will also learn how to access the IP address and DNS server for connections that must be done manually. After setting up a router, find the network security…
Internet Business Fax to Email Made Easy - With  eFax Corporate (http://www.enterprise.efax.com), you'll receive a dedicated online fax number, which is used the same way as a typical analog fax number. You'll receive secure faxes in your email, f…

815 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

11 Experts available now in Live!

Get 1:1 Help Now