[Last Call] Learn how to a build a cloud-first strategyRegister Now

x
?
Solved

172.16.0.X address: problem with VPN

Posted on 2006-06-01
17
Medium Priority
?
1,366 Views
Last Modified: 2012-05-05
Hi dear experts,

I've heard that windows "does not like" addresses with zero, like 172.16.0.X, but did not see any oficcial document about it. However, I noticed that when my station is assigned such address, VPN based on GRE protocol does not work. When address is "normal", e.g. 172.16.45.56, etc, it works. This is GPRS connection, if it helps.

Thanks in advance!
Dmitry.
0
Comment
Question by:dda
  • 6
  • 5
  • 5
  • +1
17 Comments
 
LVL 48

Assisted Solution

by:Jay_Jay70
Jay_Jay70 earned 300 total points
ID: 16805558
Hi dda,

i know what you are getting at and its due to how common the subnets are in everyday use, robwill will have the best explanation for you i will see if i can grab his attention for you
0
 
LVL 27

Assisted Solution

by:pseudocyber
pseudocyber earned 600 total points
ID: 16806508
The problem with 0's, is when an IP ends in a 0 - then it is normally a network address.

For instance, 192.168.1.0/24 (mask 255.255.255.0) this address would have to be a network (or subnet) address.

However, if the network were larger (over 256 addresses) then it might encompass a "zero" within it.  For instance, my own laptop right now.  My network is 172.16.66.0/23 which ranges from 172.16.66.1 to 172.16.67.254.  So, because I'm the network engineer and I get to pick my own IP, I took 172.16.67.0 as my IP and it works fine.

The real problem comes in with older equipment with older TCP/IP stacks which don't recognize VLSM (Variable Length Subnet Masking) - and insist that a 192.168.1.0 is a class C and can therefore only have a subnet mask of /24 and not /23 and that anything ending in .0 must be the network address.

If you have a "modern" Windows OS (like 2000, XP, 2003) this shouldn't be a problem for you.
0
 
LVL 4

Author Comment

by:dda
ID: 16806563
Thanks for suggestions. No, the address does not end in '0'. Zero is in the middle (third octet), e.g. 172.16.0.35. And yes, the OS is WinXP...
0
What does it mean to be "Always On"?

Is your cloud always on? With an Always On cloud you won't have to worry about downtime for maintenance or software application code updates, ensuring that your bottom line isn't affected.

 
LVL 27

Expert Comment

by:pseudocyber
ID: 16806580
Windows doesn't care if you have a 0 in the third octet.  If you're having an issue, I would suspect it has something to do with the VPN configuration.
0
 
LVL 78

Accepted Solution

by:
Rob Williams earned 600 total points
ID: 16808809
Nicely phrased pseudocyber.

If you are having problems with your VPN with particular addressing schemes, it may well be due to the local and remote networks having the same network ID (same subnets). Is this a possibility ? such as when both are using something like 172.168.0.x  When you do so there are routing issues, the routing devices do not know to which location to send the packets and they are usually dropped.
0
 
LVL 27

Expert Comment

by:pseudocyber
ID: 16810435
Thanks Rob.

I should have thought of the same net on both ends ... ;)
0
 
LVL 78

Expert Comment

by:Rob Williams
ID: 16811668
Early to be counting out chickens :-) we'll see if that was it or not.
--Rob
0
 
LVL 4

Author Comment

by:dda
ID: 16813832
Okay, please give me some time, and I will get back with more statistics and data. Meanwhile, is the article at http://www.easydesksoftware.com/news/news28.htm incorrect? It says:

There are a few IP addresses that are reserved for private (non-routable) networking, 192.168.0.0, 10.0.0.0, and 172.16.0.0 through 172.31.0.0. Remember that the zeros can be any number from 1 to 254. The most common private network is 192.168.0.0. The ranges are 10.1.1.1 - 10.255.255.254, 172.16.1.1 - 172.31.255.254, 192.168.1.1 - 192.168.255.254.
0
 
LVL 4

Author Comment

by:dda
ID: 16814050
I think I found the source of rumors: http://support.microsoft.com/kb/272617/en-us
It is not applicable to WinXP though. I will keep researching. Thanks to all!
0
 
LVL 27

Expert Comment

by:pseudocyber
ID: 16815513
Private addresses are "non-routable" on the Internet - they are reserved for PRIVATE internal networks.  No problems using them, until they reach a public Internet connection where they should be dropped.

If you want to know more about RFC 1918, go to the source:  http://www.faqs.org/rfcs/rfc1918.html

Interesting article @ MS - but like I said, "older TCP/IP stacks".
0
 
LVL 78

Expert Comment

by:Rob Williams
ID: 16816105
As pseudocyber stated, only a '0' as the last octet is the issue and that applies to older networking equipment, though still best to avoid them if only to avoid confusion. Usually when we discus an IP ending in zeros we are not referring to an IP address but rather a subnet ID. 192.168.1.1 with a subnet mask of 255.255.255.0  would have a network ID of 192.168.1.0  or if you had a subnet mask of 255.255..0.0 it would have a network ID of 192.168.0.0
0
 
LVL 4

Author Comment

by:dda
ID: 16831732
The problem turned out to be non-related to zeros in address. Thanks to everyone!
0
 
LVL 27

Expert Comment

by:pseudocyber
ID: 16831960
What was the problem?
0
 
LVL 4

Author Comment

by:dda
ID: 16832036
Well, it is not nailed down yet, but default gateway was not assignned sometimes. I'm creating GPRS connection, and ipconfig shows empty space in the 'Default gateway' in some cases. My IP address and DNS servers are assigned properly, but no default gateway.. Obviously, VPN connection can't work with such setup. :)
0
 
LVL 78

Expert Comment

by:Rob Williams
ID: 16832145
Thanks dda.  What is assigning the addressing information ? Would it be better, or can you assign static connection information ?
0
 
LVL 4

Author Comment

by:dda
ID: 16832268
It's 4,5M cellular subscribers network. I think that Nokia GGSN is assigning addresses, and static addresses is not an option. Actually, it should be a separate paid service ("public IP address"), and we are going to provide it. I work for that cellular network actually. :)

Cheers,
Dmitry.
0
 
LVL 78

Expert Comment

by:Rob Williams
ID: 16833151
I guess then the DHCP server configuration and functionality is out of your hands to some degree. Sorry not much help with that part.
--Rob
0

Featured Post

What does it mean to be "Always On"?

Is your cloud always on? With an Always On cloud you won't have to worry about downtime for maintenance or software application code updates, ensuring that your bottom line isn't affected.

Question has a verified solution.

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

This is the first one of a series of articles I’ll be writing to address technical issues that are always referred to as network problems. The network boundaries have changed, therefore having an understanding of how each piece in the network  puzzl…
Are you one of those front-line IT Service Desk staff fielding calls, replying to emails, all-the-while working to resolve end-user technological nightmares? I am! That's why I have put together this brief overview of tools and techniques I use in o…
This Micro Tutorial will teach you how to add a cinematic look to any film or video out there. There are very few simple steps that you will follow to do so. This will be demonstrated using Adobe Premiere Pro CS6.
Michael from AdRem Software explains how to view the most utilized and worst performing nodes in your network, by accessing the Top Charts view in NetCrunch network monitor (https://www.adremsoft.com/). Top Charts is a view in which you can set seve…
Suggested Courses

830 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