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Home Networking Problem

My friend has a home network that has worked fine for about 2 years then it started to act funny but only on his pc.  The other two (one wired, one wireless) work fine.  He has a linksys WRT54G v. 3.1 router and has recently updated to version to 4.30.5.  Almost everytime he logs on a new IP address is assigned.  Sometimes when downloading the download will stop completely and won't continue.  In the event viewer I found this error:

Event Type:      Error
Event Source:      Tcpip
Event Category:      None
Event ID:      4199
Date:            12/1/2006
Time:            8:49:44 PM
User:            N/A
Computer:      JBIRD
Description:
The system detected an address conflict for IP address 192.168.1.101 with the system having network hardware address 00:13:CE:17:51:25. Network operations on this system may be disrupted as a result.

OR

Event Type:      Warning
Event Source:      Dhcp
Event Category:      None
Event ID:      1005
Date:            12/1/2006
Time:            8:55:20 PM
User:            N/A
Computer:      JBIRD
Description:
Your computer has detected that the IP address 192.168.1.101 for the Network Card with network address 000CF18488A0 is already in use on the network. Your computer will automatically attempt to obtain a different address.

My friend has tried to disable his firewall (ez Armor) but after he does and then restarts, the internet doesnt work at all.  He has also tried resetting his router and reinstalling the firmware with no luck.  Any help would be greatly appreciated.  Thank you.
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orangutang
Asked:
orangutang
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7 Solutions
 
thur6165Commented:
Possible that firewall software has screwed up the OS, if xp try a system restroe under the system tools to back before the issue started.  More remotly could be a hardware issue.  Also might want to try assigning an ip manually and see if that bypasses the issue.
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lrmooreCommented:
>an address conflict for IP address 192.168.1.101
Apparently the other PC has this IP address manually assigned.
Try setting the DHCP settings in the Linksys to start at perhaps .200 instead of the default .100
Then this PC should get a .200 or .201 IP address

Else, just manually assign this PC a different IP, say .99 which is below the default dhcp range and should not conflict with anything else.
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WGhenCommented:
Unplug the router for a few seconds.  It will lose its dhcp table, and all the devices will be forced to request a new IP.  If the problem returns, I would recommend gathering all the legitimate mac addresses that are expected on your friends network.  In the router, under status/local network you can view the DHCP clients table.  See what you see there.  Are alll the addreses there ones you expect to see?

If that event log mac address is an unknown mac, then filter it out, under wireless/wireless mac filter.  Has he assigned any static IP addresses to anything?  Printer?

WGhen

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jekl2000Commented:
If you are using wireless, it could be that someone is spoofing your mac address and is using the wireless system. I would disable the wireless ( this can be done where you select use G only, B and G or disable wireless. Then using just and ethernet cable, see if the probalm goes away.
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JRockSolidCommented:
There are 2 different MAC addresses here but only one PC

Below are the two MACs
00:0C:F1:84:88:A0  Intel Corporation
00:13:CE:17:51:25  Intel Corporate    ?????

Do you have more than one NIC or Virtual NIC in the pc named JBIRD or is there a second PC named JBIRD?
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The_PC_DocCommented:
This is a common occurance with using wires and wireless PC's.  What is happening, your wireless PC's are getting assigned an IP Address that normally the wired PC uses.  And your wired PC is expecting it but when it starts, rather than dynamically reassigning itself a new one, it stil keeps the old one.  I been finding this a lot on PC's that habe not been updated to Service Pack 2.

First, make sure all PC's have been updated to SP2 (If you can).

Then create a static IP address on the wired PC.  Use 192.168.1.1 as the default gateway, use 192.168.1.120 as the IP address if the PC, SubNet of 255.255.255.0.  You are going to have to get the DNS Server 1 and 2 information from the Status Page in the router.  Put that info into the respective spots in the Static IP page and hit Apply and OK.  Restart the PC and you are all set.

Good Luck!!
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orangutangAuthor Commented:
Okay, well I'll tell my friend that later but for more information, he has 2 wired computers, one with Windows Me, one Windows XP SP2. The other computer is a Mac laptop that's wireless.
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The_PC_DocCommented:
Thanks for the update.  With that added info, it may now explain what is going on.  Windows ME and the MAC, though are supposed to be DHCP capable, and because you are using 3 different OS's, there may be some issue with them autonegotiating.

I would set up static IP's on all wired machines.  Set them at least 20 numbers higher than what the DHCP is set to start at.  This will stop any further problems from occuring and allow the wireless networking to continue and add as many as 20 other systems onto the network wirelessly without the wired PC's causing problems.

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Leon FesterIT Project Change ManagerCommented:
If things have been working fine for such a long time...then consider the following:
How secure is the wireless network? Could there be unathorized access to the wireless network?

You say that your friend has a home network, I'm then assuming no domain controller so dhcp access provided by router?

Your error message above gives us the MAC addresses of the machine with the duplicated IP address. You can check if there machines actually belong to your friend by a simple test.

On each machine(assuming all are Windows 95 or higher OS), run the following command at a command prompt:
ipconfig /all

What you're looking for is listed under the heading: PHYSICAL ADDRESS, under the adapter section:
e.g.  
The system detected an address conflict for IP address 192.168.1.101 with the system having network hardware address 00:13:CE:17:51:25.

Your computer has detected that the IP address 192.168.1.101 for the Network Card with network address 00:0C:F1:84:88:A0 is already in use on the network. Your computer will automatically attempt to obtain a different address.
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Leon FesterIT Project Change ManagerCommented:
ACK! Finger problems...reposting....

If things have been working fine for such a long time...then consider the following:
How secure is the wireless network? Could there be unathorized access to the wireless network?

You say that your friend has a home network, I'm then assuming no domain controller so dhcp access provided by router?

Your error message above gives us the MAC addresses of the machine with the duplicated IP address. You can check if there machines actually belong to your friend by a simple test.

On each machine(assuming all are Windows 95 or higher OS), run the following command at a command prompt:
ipconfig /all

What you're looking for is listed under the heading: PHYSICAL ADDRESS, under the adapter section:
e.g.  00-13-ce-17-51-17

If any adapter reports the same address as listed above(or below), then you've found the machine that is getting the duplicate IP Address.
00:13:CE:17:51:25
00:0C:F1:84:88:A0
P.S. Sometimes MAC addresses are written without seperators, or with either colons(:) or hypens(-)

If none of the adapters have matching physical addresses then consider the possibility that the offending machine is gaining unauthorized access to your friends network.

P.S. Any chance that your fried added other devices to the network? xbox/psp/playstation/pda/etc,(even some modern fridges already have LAN connections) can all access wireless networks. The device does NOT have to be a PC.
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WGhenCommented:
A couple of points...
1.  Linksys routers by default begin handing out IP addresses at 100, so if you are going to use some static addresses they should be BELOW 100; ex. 192.168.1.20.
2.  I have NEVER had my linksys routers hand out duplicate addresses whether or not they are wired, wireless, different OS etc.  I currently have one Win2K, one WinXP, and one Mac.
     This is because the DHCP server should ping an address before giving it out.
2a. If for some reason a device has an address but won't respond to a ping (personal firewall: Symantec or ZoneAlarm etc.?) then a duplicate could be given out.
3.  As I mentioned above, identifying what MAC addresses you have goes a long way towards identifying whether or not the duplicate IP device even belongs to you, meaning you might have a security problem.
3a. So far no mention has been made about what if any security is running.  These questions lead me to suspect we might be looking at an out-of-the-box set up, meaning NO security.
     Turning some kind of security on might help.  Even changing the default SSID and turning off the "Broadcast SSID" option might fix this.  My stepdaughter has moved several times and when she does, she always turns on her laptop to see if she has free wireless internet to tide her over until the cable guy comes.
4.  Oh heck... Three is enough for now.

WGhen
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orangutangAuthor Commented:
Also, I think he got his router a couple of years ago and he got his laptop about a year ago and he never had any problems until he reformatted his HD. I've sort of had a weird problem where my router assigned me another IP address after I reformatted my HD but I haven't had any problems.
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The_PC_DocCommented:
WGhen, though your comment is true about the router handing out IP's, there are times the PC will not take the IP assigned and keep the old one causing conflicts with other PC's on the network that are taking the assinged IP's.  This has happened to me in the field more times then I can count.

MAC filtering via router can go a long way with security.  It is a very valid point and should be addressed.

As for software firewalls, turn them off till you resolve the issue.  Then turn them on and deal with it after.  Stick to one problem at a time.
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orangutangAuthor Commented:
Oh, my friend hasn't had any problems for a while and I don't think he tried any of these solutions. Sorry, I'll figure something out for your hard work.
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