error message - 2 computers using same ip address

Avatar

Please consider registering
Guest

Search

— Forum Scope —






— Match —





— Forum Options —





Minimum search word length is 3 characters - maximum search word length is 84 characters

Register Lost password?
sp_Feed sp_topic_old
error message - 2 computers using same ip address
Avatar
starchy
Ottawa ON, Canada
Member
Forum Posts: 25
Member Since:
November 17, 2008
sp_UserOfflineSmall Offline
1
May 24, 2011 - 10:03 pm
sp_Permalink sp_Print

My wife and I each have new laptops running Win 7 Home premium. Our internet connection is a MiFi on our local cell phone network, as the only other choice is satellite, which we used for 9 years and was less than satisfactory. This MiFi allows up to 5 wireless connections to the internet, and most of the time we have only hers connected, but at times, 2 or 3 at a time, the 2 laptops and an iPad2. Recently her laptop, a Dell with i5, (mine is an Asus i3) has been getting a Windows error message that another device is using the same IP address. I Googled this and checked both computers through IP Config to ensure that Dynamic "something" was on and it was on both, yet they were using the same IP address.
My questions are;
Is this a problem?
How do I resolve the conflict?
Given my rudimentary geek knowledge, is the MiFi creating this problem, and if so does this mean that it is defective?

Trusting that you know what a MiFi is, if not, it is a cell (wireless phone) connection and wireless router to the internet. Fast enough, but a 5GB monthly limit.
Thanks for any and all replies.

"Do Something. If it works, do more of it. If it doesn't, do
something else." - FDR

Avatar
Chad Johnson
Mod
Forum Posts: 867
Member Since:
August 11, 2011
sp_UserOfflineSmall Offline
2
May 24, 2011 - 11:25 pm
sp_Permalink sp_Print

Hiya!

Never used a mifi before, but the concept is certainly similar. The mifi should be handling the delegation of IP addresses and making sure that no two computers get the same IP address. Obviously, that didn't work.

This can happen on any network when a computer is asleep, and while asleep the IP address is handed to another computer. When the computer wakes up, it doesn't ask for a new address, just grabs the one it had.

A few ways to resolve this --

1) Turn off each computer and power them up one by one. This [b:2rwhzyf5]should[/b:2rwhzyf5] have them each ask for a new IP address.
2) If that doesn't work, pick your favorite computer and click the Start Orb. Type 'cmd' in the search box. When Command Prompt appears, right click and select 'Run as Administrator'. In the black screen that appears, type
[code:2rwhzyf5]ipconfig /release[/code:2rwhzyf5]
Then
[code:2rwhzyf5]ipconfig /renew[/code:2rwhzyf5]
This will kick you off your network until the commands are finished running.

If neither of those options work post back and I'll guess some more.

Avatar
starchy
Ottawa ON, Canada
Member
Forum Posts: 25
Member Since:
November 17, 2008
sp_UserOfflineSmall Offline
3
May 25, 2011 - 2:08 pm
sp_Permalink sp_Print

Ziggie,
Wow, thanks a lot. You seemed to have nailed it. Just a few minutes ago I booted my laptop, and my wife's was indeed asleep, and lo and behold, when she woke her computer up, she got the error message. Checked again and we did have the same IP address. I restarted mine and checked again and they were different. So from now on, I will get her to wake hers up before I boot mine. To your knowledge, does having the same IP address cause any problems?
Thanks again for your spot on explanation!

"Do Something. If it works, do more of it. If it doesn't, do
something else." - FDR

Avatar
Chad Johnson
Mod
Forum Posts: 867
Member Since:
August 11, 2011
sp_UserOfflineSmall Offline
4
May 25, 2011 - 10:24 pm
sp_Permalink sp_Print

To your knowledge, does having the same IP address cause any problems?
[/quote:soneljrb]

Yes!!

Here's a brief overview of Networking 101:

Computers talk to each other using IP addresses.
People talk to each other using names.
DNS is the phone book of the Internet that translates Name to IP address.
When you ask for google.com the following things occur:
[list:soneljrb]
Computer goes to a DNS server (your mifi in this case, your home internet router in most cases) and says "I want google.com, what's their ip address?"
Mifi/router/whatever either answers with ah-ha, here it is (recent requests are cached), or...says hold on, let me look it up.
Mifi/router/whatever asks its connection (probably your ISP) for the IP address.
Your ISP says (usually): "I don't know, but I do know server x.x.x.x has that"
Mifi/router/whatever asks server x.x.x.x for IP address.
Server x.x.x.x responds with IP address.
Computer directly asks IP address for the web page.
[/list:u:soneljrb]
Can multiple names have the same IP address? Certainly. But whatever answers on the other end (back to the telephone metaphor) has to know how to get the call to the right person. So when you 'dial' the IP address, the server that answers says "Hey Google, it's for you".

Great for the Internet, but what about your local network?

Every time you make a connection through your mifi/router/whatever - that device is keeping track of the connection request. So when it sends out the request for Google, and Google responds, the mifi/router/whatever knows which computer to give the information back to.
If both your comptuers have the same IP address, then your mifi/router/whatever doesn't know what computer to give the information back to. Likely it will send it to both so things will keep working.

This increases load on your local network (not the Internet side) and can slow things down if there is a lot of traffic being sent everywhere because the mifi/router/whatever doesn't know where to send the information.

So! Here is a very long explanation to say that yes it matters, not as much as people may think, but enough that you probably don't want to keep the scenario.

(if you are interested, here's a [url=http://tldp.org/HOWTO/Unix-and-Internet-Fundamentals-HOWTO/internet.html:soneljrb]link[/url:soneljrb]to give you even more information)

As for long term fixes -- I don't know what kind of settings your Mifi has on it, but what is happening here is the "IP lease" isn't long enough for the Mifi to reserve the IP address for any length of time. So when laptop A goes to sleep, it happily gives the IP address of laptop A to laptop B.

Avatar
starchy
Ottawa ON, Canada
Member
Forum Posts: 25
Member Since:
November 17, 2008
sp_UserOfflineSmall Offline
5
May 26, 2011 - 9:27 pm
sp_Permalink sp_Print

I love your explanation in layman's terms of what is going on, it is a lot clearer to me now. What a great reference for others who want to have some idea what is going on. Who knew so much goes on when I simply type google.com into my address bar? Amazing that it happens so fast as well. I had no idea that all of this happens. Whoever figured all of this out so that it happens every time a user goes to a web site must truly be a genius! Way beyond me.
Further to what I reported happening yesterday, just a few minutes ago, my wife was surfing perfectly well, and I booted my laptop. As soon as my computer logged on to the MiFi (actually a modem and router in one, that connects to the net via cell phone system, and about the size of a deck of cards only 1/2 as thick, allowing up to 5 wireless connections at a time), she got the error message that she had an IP Address conflict. So we both ran CMD then IPCONFIG and hers was 192.168.1.3 and mine was 192.168.1.2 so in fact, according to that test, there was no conflict yet she rec'd the error message. We checked our Ipod Touch and Ipad2 and they were both off, not sleeping, but off. So does this mean that we have a Windows problem or a MiFi problem? We have never had a problem with hers or my computer receiving the other's web site request though. I checked a web site - http://www.whatismyipaddress.com on both machines and got totally different addresses - 184.151.127.215 for both computers. Even though IPCONFIG gives different addresses from within the 2 computers, is the conflict referring to the fact that out there in the web, both machines seem to have the same address. Or is the 184.151.127.215 the web address that our MiFi modem/router uses at the time to access the web?
If my questions are frivolous and really splitting hairs, I am OK with you telling me that, and I will not worry about the whole issue given your explanation in your last post. I guess I am trying to figure out if I have a problem with my modem/router or Windows, and if I really need to take action to correct anything. Thanks again for your time to explain to me (and hopefully others) about what really happens when we access the web.

"Do Something. If it works, do more of it. If it doesn't, do
something else." - FDR

Avatar
Chad Johnson
Mod
Forum Posts: 867
Member Since:
August 11, 2011
sp_UserOfflineSmall Offline
6
May 26, 2011 - 10:14 pm
sp_Permalink sp_Print

No worries - the only silly questions are the ones never asked. How else do you learn?

Was your computer hibernated / sleeping / or shut down?
Where there no other devices turned on using your mifi?

Here's what I think happened: Your computer was on earlier, and had IP address 192.168.1.2. Your computer went to standby / sleep / hibernation but held on to its IP address internally. The mifi, seeing your computer no longer connected, happily handed IP address 192.168.1.2 to your wife's computer when she connected.

When your computer came back on, it told the network "Hi, I'm 192.168.1.2.". Your wife's computer, upon receiving this message, declared "If he's 192.168.1.2, I can't be. I need a new IP address." So your wife's computer requested a new IP address from the mifi (192.168.1.3) and notified your wife that there was an IP address conflict.

Can this be stopped? Not really sure having never used a mifi. Is there a settings screen where you can go and configure wi-fi settings? Look for a setting called DHCP Lease Time or something similar and see what it's set to. It's likely quite low.

As for the other question...

every device on the network has an address. Unfortunately, there are only about 4.3 billion addresses available to the public Internet. With cell phones, laptops, mifis, refrigerators, light bulbs, toasters, ovens, socks, etc all coming online, frequently these things are getting there own address out of the 4.3 billion address pool. All that times 7 billion people and we can quickly run out.

Several of these blocks are reserved for private networks (they tend to start with 10. or 192.) These are duplicated many times around the world but [b:moanvvy8]cannot be accessed[/b:moanvvy8] from the Internet.

A device called a router (your mifi, my wireless router, etc) sits between the Internet and your local network. In our phone book example above, this is the answering machine (or a front door). On one side is the Internet and everyone and everything on it. To that side of it you are known as 184.151.127.215. On the other side, the router knows that your computer is 192.168.1.2 and your wife's is 192.168.1.3 and your ipod is 192.168.1.4 etc.

So -- all the traffic that leaves your network -- to the rest of the world it all originates from your public facing address.

HTH...

Avatar
starchy
Ottawa ON, Canada
Member
Forum Posts: 25
Member Since:
November 17, 2008
sp_UserOfflineSmall Offline
7
May 26, 2011 - 10:41 pm
sp_Permalink sp_Print

Thanks once more for your clear and detailed explanation. To answer your question, this time, her computer was active and she was doing email and Facebook. Then I booted up and then she got the conflict message. When I first posted, indeed her computer was asleep, and when she woke it up it gave her the error message. Not this time though, it was active when I booted. Thanks for the explanation about the difference between the 192 xxx and 184 xxx IP addresses.

"Do Something. If it works, do more of it. If it doesn't, do
something else." - FDR

Avatar
David Hartsock
Admin
Forum Posts: 1105
Member Since:
August 7, 2011
sp_UserOfflineSmall Offline
8
May 27, 2011 - 11:12 am
sp_Permalink sp_Print

Chad,

I commend you on your excellent explaination! Truly a great asset to DCT! I'll give you two gold stars.

Starchy,
Ipad? We can't have any discussion about the forbidden fruit company on DCT! - Just Kidding!!!!

Have a look in the MiFi manual (if you have one) and follow Ziggie's advice about DHCP lease. Likely that is the cause (and cure) for the issue.

Avatar
Chad Johnson
Mod
Forum Posts: 867
Member Since:
August 11, 2011
sp_UserOfflineSmall Offline
9
May 27, 2011 - 11:21 am
sp_Permalink sp_Print

Chad,

I commend you on your excellent explaination! Truly a great asset to DCT! I'll give you two gold stars.
[/quote:o998zj3w]

Oooo....a raise!

Avatar
starchy
Ottawa ON, Canada
Member
Forum Posts: 25
Member Since:
November 17, 2008
sp_UserOfflineSmall Offline
10
May 27, 2011 - 3:25 pm
sp_Permalink sp_Print

Dave,
I like your suggestion about consulting the manual for the MiFi, except that what came with it was simply an installation pamphlet which has no usable info in it. I will research the unit online, and if not successful, I will pursue the matter with the supplier, Bell Canada. I am pleased that you gave Ziggie a raise to 2 gold stars, he deserves it, most heartily. As far as the "forbidden fruit company", I apologize for that, it is my wife's. It is a neat toy however, but no match for a "REAL" computer! (I have been known to play Angry Birds maybe once or twice)

"Do Something. If it works, do more of it. If it doesn't, do
something else." - FDR

Avatar
David Hartsock
Admin
Forum Posts: 1105
Member Since:
August 7, 2011
sp_UserOfflineSmall Offline
11
May 27, 2011 - 4:13 pm
sp_Permalink sp_Print

OK, I think I've found the manual. 3 things to think about...

1. change the admin password
2. Use WPA2 security
3. (if you want) use MAC filtering

I just had time for a quick glance, but didn't see a setting for DHCP lease time. You'll have to look further and you will probably want to anyway to learn a little about the device!

[url=http://www.google.com/url?sa=t&source=web&cd=1&sqi=2&ved=0CBkQFjAA&url=http%3A%2F%2Fwww3.ipass.com%2Fwp-content%2Fuploads%2F2010%2F10%2FNovatel_MiFi_UserGuide.pdf&rct=j&q=mifi%20manual&ei=1gPgTfCXA5K_gQelmoX4Cg&usg=AFQjCNG5jLeMsdhF5L_142vEfcCZIK8Kjg&sig2=IqkvvwPUzfmrCOmiHgnSlg&cad=rja:2oaadknk]MiFi user guide[/url:2oaadknk]

Avatar
starchy
Ottawa ON, Canada
Member
Forum Posts: 25
Member Since:
November 17, 2008
sp_UserOfflineSmall Offline
12
May 28, 2011 - 12:20 pm
sp_Permalink sp_Print

Hi Dave, Thanks so much for pointing me to the pdf version of the manual for the Novatel MiFi 2372. Downloaded it and read it and it is just like the paper version that came with the unit. At least I don't have to go looking for the booklet anymore, it is now on my laptop! It does not talk about DHCP lease time, and I went into the router set up page where you can see all kinds of info and change a few settings @ 192.168.1.1 but nothing about lease time and the only reference to WPA was - "Security WPA personal/PSK" - and no way I could see to modify it. We had reset the password from admin when we first hooked it up last September. I have done a preliminary search for the lease time, and found nothing, so I will write to Novatel to see if they can help. I did find out about a recall for this unit due to battery overheating so I will contact Bell Canada about that. This is a problem for us as it does get HOT and often will shut down and force us to remove the battery for a minute and reboot and it goes back online. We tend to keep it on a ceramic cup coaster on the table to act as a heat sink which seems to work quite well. this is our only internet access method, and though expensive if you go over 5 GB, it is so much better than our only other options, satellite or dial up. We just have to avoid You Tube and large downloads to keep out costs manageable. Couldn't do You Tube on satellite anyway, too slow, so "You never miss what you never had", kind of applies for us. Thanks again for your help and time to write answers. As well, for maintaining and administering the forum. This is my "Goto" place for help. I just wish I could give back somehow, but I know just enough to get me into trouble.

"Do Something. If it works, do more of it. If it doesn't, do
something else." - FDR

Avatar
meem
Member
Forum Posts: 1
Member Since:
June 6, 2011
sp_UserOfflineSmall Offline
13
June 6, 2011 - 2:38 pm
sp_Permalink sp_Print

Hi,

I am having a similar problem. I work for a company that has multiple computers connected to a network. One of the computers we rarely use says it has the same IP address as another computer.

When I initially start this computer I can use the internet and access programs on our newtork only for a few minutes before I get kicked off. If I reset the IP will I lose connection to our network? I don't want to mess with it too much. This seems like a quick fix that could be very helpful, but if it means everything will have to be reconfigured I should probably call the real Tech guys.

Avatar
Chad Johnson
Mod
Forum Posts: 867
Member Since:
August 11, 2011
sp_UserOfflineSmall Offline
14
June 7, 2011 - 11:18 am
sp_Permalink sp_Print

In a corporate environment, there are many different variables that could contribute to that.
To even begin to guess, we'd need to know things like:
* Are you using a DHCP server?
* Is this computer configured with a static address?
* Is another computer configured with a static address?
* What authentication protocols are running on your network?
* Is this wireless or wired?
* When did it last work correctly?

Some of this we could probably answer by poking around on the computer. Others, you would need your IT folk involved. Without knowing more, I can't tell you what resetting the IP would do - as each corporation is different...

My best recommendation is going to be to involve your local IT.

--Zig

Avatar
gazza
SE Queensland, Australia
Member
Forum Posts: 36
Member Since:
September 16, 2008
sp_UserOfflineSmall Offline
15
July 13, 2011 - 8:39 pm
sp_Permalink sp_Print

For a small network a simple way around the problem if there is only 3 IP devices ever attached might be to give each one a permanent IP address in the range allowed by the router.
1st device could be 192.168.1.2
2nd device could be 192.168.1.3
3rd device could be 192.168.1.4
This is done by changing properties of Network connections - changing from"Obtain IP Address Automatically" to "Use the following IP Address" and type in IP Address in windows provided (this is calleda Static IP Address). This would need to be done on each device. I have no clue as to how you would do it on the toy - Ipad.
I use a mix of Dynamic and Static IP addresses on my home network. Most routers allow you to define the range of IP addresses used for DHCP server.
Hope this helps and you can understand - if not please ask if you need more help.

I used to do Network Architect design and corporate networks are a lot more complicated than home networks. Having two PCs with same IP address can cause a major disruption to a network. We had special PCs that would monitor network to ensure this did not happen - especially when the network had 60,000 PCs (2500 in building I was in), hundreds of files servers, Unix mins and IBM/Fujitsu mainframes. I early days duplicate IPs could bring a network segment down.

Success is the ability to go from one failure to another with no loss of enthusiasm. (Winston Churchill)

Forum Timezone: America/Indiana/Indianapolis

Most Users Ever Online: 188

Currently Online:
6 Guest(s)

Currently Browsing this Page:
1 Guest(s)

Member Stats:

Guest Posters: 10

Members: 1273

Moderators: 3

Admins: 4

Forum Stats:

Groups: 8

Forums: 19

Topics: 1538

Posts: 11824

Administrators: Jim Hillier, Richard Pedersen, David Hartsock, Marc Thomas

Moderators: Judy Novotny, Jason Shuffield, Mail Poet