Question

using public IPs for internal network + NATing

Asked by: Infinite_Recursion

I am on a network with the following specs:
1- Default Gateway with local IP of 12.12.12.1
My machine with an IP of 12.12.12.246 mask= 255.255.255.0 (I guess that means there is subnetting)
3- the Gateway has another Public IP on the other interface, so basically we don't own the 12.12.12.1 - 12.12.12.254 subnet at all, and I am guessing that a 12.0.0.0 network is of class A, so basically the original mask would be 8 bits 255.0.0.0. My question is, does sub-netting this way make the IP private? Would using this configuration not cause problems? What if I wanted to connect to the actual System on the Internet that has the 12.12.12.1 - 12.12.12.254 IP what happens then?

This Question has been solved and asker verified All Experts Exchange premium technology solutions are available to subscription members.

Subscribe now for full access to Experts Exchange and get

Instant Access to this Solution

  • Plus...
  • 30 Day FREE access, no risk, no obligation
  • Collaborate with the world's top tech experts
  • Unlimited access to our exclusive solution database
  • Never be left without tech help again

Subscribe Now

Asked On
2007-11-02 at 02:09:20ID22934288
Tags

public

,

network

,

using

,

ip

,

internal

Topics

TCP/IP

,

Windows NT Networking

Participating Experts
2
Points
500
Comments
8

Trusted by hundreds of thousands everyday for fast, accurate and reliable tech support.

  • "The time we save is the biggest benefit of Experts Exchange to Warner Bros. What could take multiple guys 2 hours or more each to find is accessed in around 15 minutes on Experts Exchange." Mike Kapnisakis, Warner Bros.
  • "Our team likes having a resource that is more secure than just using Google and most experts using this service really know their stuff. It's nice to look here first versus using Google." Dayna Sellner, Lockheed Martin
  • "Anytime that I've been stumped with a problem, 9 out of 10 times Experts Exchange has either the accepted solution or an open discussion of the potential solution to the problem." Kenny Red, eBay Inc.

See what Experts Exchange can do for you.

Got a question?

We've got the answer.

Experts Exchange has been collecting answers to technology questions since 1996…3 million and counting! If you have a question, chances are we already have your answer.

Screenshot of Experts Exchange Knowledgebase

Need individual assistance?

Our experts are ready to help.

If you can't find the exact answer you're looking for, ask our exclusive community of 50,000 experts. You’ll get a personalized answer from a trusted professional.

Screenshot of Experts Exchange Knowledgebase

Want to learn from the best?

Read articles from industry experts.

Thousands of free tech tips, tricks, how-to’s and tutorials are available in our peer reviewed articles section. See for yourself how smart our experts are, no login required.

Screenshot of an Article

Working on a long term project?

Store your work and research.

Save solutions to your questions, answers you’ve discovered through searching plus helpful articles in your personal knowledgebase for easy future access.

Screenshot of Experts Exchange Knowledgebase

Access the answers to your technology questions today.

Subscribe Now

30-day free trial. Register in 60 seconds.

What Makes Experts Exchange Unique?

Members of the expert community talk about why the experience at Experts Exchange is different than what you will find anywhere else.

Trusted by the world's most respected brands.

image of each brand's logo

Faithfully serving IT professionals since 1996.

Experts Exchange Logo

Try it out and discover for yourself.

Subscribe Now

30-day free trial. Register in 60 seconds.

Related Solutions

  1. Subnet masking
    Hi all, I need help with subnet masking on win2k server. Before we start please don't direct me to unhelpful links. I'd prefer your own explanation. Let's say currently there are about 150 clients logging onto win2k running DHCP. Subnet mask is 255.255.255.0. In a few mo...
  2. Finding Public Ip / Subnet Mask / Gateway / DNS
    Hello experts, I would like to know what my public IP address, subnet mask, gateway and DNS address are on the public side (not LAN). Is there any way to do that aside from calling up the ISP?
  3. VPN's and Nating
    If I have setup to nat a device from an internal ip address to an external ip address and this device is part of a VPN (site-to-site), and I setup another separate VPN from this same internal device to a remote device (site-to-site), but with this VPN I don't want to nat the ...
  4. Subnet mask
    ok here is the setup: Time Warner 10Mb ethernet connected to a SonicWall 2040 PRO, IP-207.250.57.230 Email Server connect to the DMZ port.. IP - 207.250.161.1 what subnet mask should I use so that people can communicate with the server? if i set the WAN and server subnet ma...
  5. subnet mask
    Is it all separate subnet must be equal if i have 223.1.17.0/24 If I want subnet a 125 interface subnet b 60 interfaces subnet C 45 can i just separate Network boardcast 223.1.17.0 223.1.17.1 223.1.1...

Free Tech Articles

  1. WARNING: 5 Reasons why you should NEVER fix a computer for free.
    It is in our nature to love the puzzle. We are obsessed. The lot of us. We love puzzles. We love the challenge. We thrive on finding the answer. We hate disarray. It bothers us deep in our soul. W...
  2. SCCM OSD Basic troubleshooting
    SCCM 2007 OSD is a fantastic way to deploy operating systems, however, like most things SCCM issues can sometimes be difficult to resolve due to the sheer volume of logs to sift through and the dispe...
  3. Migrate Small Business Server 2003 to Exchange 2010 and Windows 2008 R2
    This guide is intended to provide step by step instructions on how to migrate from Small Business Server 2003 to Windows 2008 R2 with Exchange 2010. For this migration to work you will need the fo...
  4. Create a Win7 Gadget
    This article shows you how to create a simple "Gadget" -- a sort of mini-application supported by Windows 7 and Vista. Gadgets can be dropped anywhere on the desktop to provide instant information, ...
  5. Outlook continually prompting for username and password
    There have been a lot of questions recently regarding Outlook prompting for a username and password whilst using Exchange 2007. There are a few reasons why this would happen and I will try to cover t...
  6. Backup Exchange 2010 Information Store using Windows Backup
    There seems to be quite a lot of confusion around the ability to backup Exchange 2010 using the built in Windows Backup feature. This stems from the omission of this feature prior to Exchange 2007 s...

Cloud Class Webinars

  1. Avoiding Bugs in Microsoft Access
    Alison Balter takes and in-depth look at avoiding bugs in Access. In this webinar you will learn about using the immediate window to debug your applications, invoking the debugger, using breakpoints to troubleshoot, stepping through code, setting the next statement to execute, ...
  2. Top 10 Best New Features in Visio 2010
    Scott Helmers gives live demonstrations of the top 10 new features in Visio 2010. This webinar will teach you how to create compelling diagrams by adding shapes to the page with a single click, linking the shapes in a diagram to data in Excel (or SQL Server, or SharePoint), ...
  3. IT Consultant Business Secrets Revealed
    Michael Munger, Experts Exchange tech pro and IT consultant, pulls back the curtain on his very successful businesses and answers question on every IT consultant and business owner should know about. He shares secrets on what he did to solve the 5 most common problems in IT, ...
  4. Disaster Recovery and Business Continuity
    Quest CTO, Mike Billon, gives an overview of the steps involved in building a dunamic disaster recovery plan. Through case studies and an examination of software/hardware tooles for monitoring and testing, you'll gain a better understandin of where you are, where you want ...
  5. Organize Your Visio Diagrams with Containers and Lists
    Scott Helmers uses cross functional flowcharts, wireframe diagrams, data graphic legends and seating charts to teach you: how to ustilize all three new structured diagram components in Visio 2010, the best practices for organizeing shapes in previous version of Visio, how to organize ...
  6. How to Us Objects, Properties, Events and Methods in Microsoft Access
    Alison Dalter gives an in-depbth look at objects, properties, events and methods in Microsoft Access. In this webinar you will learn about using the object browser, referring to objects, working with properties and methods, working with object variables, understanding the ...

Join the Community

Give a Little. Get a Lot.

Join the community of experts here and help other tech pros by answering question in your area of expertise. You can earn FREE access to all Experts Exchange's premium features and resources.

Join the Community

Answers

 

by: oBdAPosted on 2007-11-02 at 02:33:16ID: 20199078

No, it doesn't make the IP range you're using private.
Yes, it will cause problems, because you're not able to access any host that has a "real" IP address that's in "your" range.

IP address
http://en.wikipedia.org/wiki/IP_address

Classful network
http://en.wikipedia.org/wiki/Classful_network

The 12.x.x.x range is AT&T, by the way:

AT&T WorldNet Services ATT (NET-12-0-0-0-1)
                                  12.0.0.0 - 12.255.255.255
Alascom ALASCOM-12-0 (NET-12-12-0-0-1)
                                  12.12.0.0 - 12.12.127.255

# ARIN WHOIS database, last updated 2007-11-01 19:10
# Enter ? for additional hints on searching ARIN's WHOIS database.

 

by: ubigPosted on 2007-11-02 at 02:43:34ID: 20199116

The Internet Assigned Numbers Authority (IANA) has reserved the following three blocks of the IP address space for private internets:
10.0.0.0        -   10.255.255.255  (10/8 prefix)
172.16.0.0      -   172.31.255.255  (172.16/12 prefix)
192.168.0.0     -   192.168.255.255 (192.168/16 prefix)
I would recommend to stick with those address spaces.
What would happen if you connect to the actual system on the Internet that has the 12.12.12.1 - 12.12.12.254 would depend on your router. In most cases router would get lost and you would be not able to communicate with that subnet

 

by: Infinite_RecursionPosted on 2007-11-02 at 02:53:43ID: 20199147

Could that configuration cause software like for example Intel VIIV Media Server to go wacko??

 

by: ubigPosted on 2007-11-02 at 02:57:05ID: 20199159

Software itself should have not any problems with your IP network configuration. But routers could.

 

by: Infinite_RecursionPosted on 2007-11-02 at 03:11:25ID: 20199204

Ok thanks guys, just one final question, does the router not take into consideration the mask when routing packets? Or that mask is just to define the broadcast domain? And why would my connection still work if I change the mask to something like 255.255.0.0??

 

by: oBdAPosted on 2007-11-02 at 03:27:38ID: 20199246

The netmask defines which packets are local and which have to pass through the router (the netmask is defined in your router as well, btw.).
And why shouldn't your connection still work if you change the netmask to 255.255.0.0? The only effect as far as your external connection is concerned would be that the range of real IP addresses you can't reach would be significantly larger.

 

by: Infinite_RecursionPosted on 2007-11-02 at 03:36:35ID: 20199270

OK, but if I change the mask on the client machine should it not also be changed on the Router in order for it to work? Meaning if I have a 24 bit mask on the Router and a 16 bit mask on the client would that still work? since the changes I made and tested were only on the client.

 

by: oBdAPosted on 2007-11-02 at 03:44:14ID: 20199291

The router and all clients should have the same netmask, otherwise you can expect weird results; depending on what the target address is, it will still work (as you noticed).

20120131-EE-VQP-002

3 Ways to Join

30-Day Free Trial

The Experts

98% positive feedback on 31,087 answers since March 2000. angeliii is a Microsoft Most Valuable Professional for his work with MS SQL Server & Develoment.

He has also proven his knowledge of Visual Basic Programming, PHP Scripting and Oracle Databases.

The Experts

97% positive feedback on 10,752 answers since July 2000. lrmoore has more than 18 years experience in the networking industry.

The six-time Mircosoft MVPs specialties include firewalls, virtual private networking, and network management.

Testimonials

"...and excellent source for support... Kind of like having your very own IT dept." Electriciansnet

Testimonials

"I was apprehensive at signing up at first. However... it has already made my life as an IT administrator much easier." JaCrews

Testimonials

"WOW! You guys have great, active, and knowledgeable people on here." moore50

Business Clients

Business Clients

In the Press

"If you’ve got a question... Experts Exchange can supply an answer.”

In the Press

"...an invaluable aid for both IT professionals and those who require tech support."

In the Press

"where IT professionals provide quick answers on just about any topic"

Business Account Plans

Loading Advertisement...