Want to protect your cyber security and still get fast solutions? Ask a secure question today.Go Premium

x
  • Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 323
  • Last Modified:

Subnetting_why are these two subnets talking?

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
valmatic
Asked:
valmatic
  • 3
  • 3
  • 2
  • +1
2 Solutions
 
MorDrakkaCommented:
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
 
valmaticAuthor Commented:
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
 
JohnjcesCommented:
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
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!

 
valmaticAuthor Commented:
THanks guys,  Guess that answers my question. :)
0
 
MorDrakkaCommented:
WHAT ? I believe I answered it. Johnices even gives the same link as I do.
0
 
JohnjcesCommented:
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
 
Rob WilliamsCommented:
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
 
JohnjcesCommented:
valmatic

I do concur with RobWill!

John
0
 
valmaticAuthor Commented:
points split.  
0

Featured Post

Visualize your virtual and backup environments

Create well-organized and polished visualizations of your virtual and backup environments when planning VMware vSphere, Microsoft Hyper-V or Veeam deployments. It helps you to gain better visibility and valuable business insights.

  • 3
  • 3
  • 2
  • +1
Tackle projects and never again get stuck behind a technical roadblock.
Join Now