Solved

Subnetting_why are these two subnets talking?

Posted on 2007-11-19
10
304 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
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
  • 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
Independent Software Vendors: We Want Your Opinion

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

 
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

Industry Leaders: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!

Question has a verified solution.

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

Suggested Solutions

Title # Comments Views Activity
Problems with VOIP phones and Comcast Business internet connection 27 134
what is mstp 6 65
IR 1023 Scanning 4 52
VLAN Issue 4 74
Don’t let your business fall victim to the coming apocalypse – use our Survival Guide for the Fax Apocalypse to identify the risks and signs of zombie fax activities at your business.
This article will inform Clients about common and important expectations from the freelancers (Experts) who are looking at your Gig.
Get a first impression of how PRTG looks and learn how it works.   This video is a short introduction to PRTG, as an initial overview or as a quick start for new PRTG users.
This video gives you a great overview about bandwidth monitoring with SNMP and WMI with our network monitoring solution PRTG Network Monitor (https://www.paessler.com/prtg). If you're looking for how to monitor bandwidth using netflow or packet s…

733 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