Weirdest network connectivity problem...


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Hi all, I am the net admin for a small firm.. and have lost all marbles on this one..

situation:

laptop is getting an IP address from the Router correctly, but cannot ping the gateway (which is the same router). Also cannot ping any LAN computers.

All firewalls are off internally, I also checked the router logs which is also the firewall for us. I dont see any problems. ICMP requests are going through the firewall/router with no problems.

Funny thing, other laptops are working good with the same router/firewall.

I reinstalled the driver, updated the driver, disabled the LAN port on laptop, also tried with giving static IP address to the laptop through router/firewall... Still same issue.

Most interesting part, it does work for a few seconds at random time, but then if tried again, cannot ping anything.

I know the wireless card is fine because this worked perfectly on outside networks.

I dont see any particular settings on out internal wireless lan that may cause this.

Its Lenovo laptop with Win7 Pro.2bit, using realtek wireless card. again the card is

Any idea whats happening? :)
 

TrainableMan

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Is there any Anti-virus software installed? If there is an AV, does it have it's own firewall that may need disabled or opened?
 
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Kougar

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Howdy Skydiver!

I am not a networking expert, and you have already covered all the bases I can think of! I'll offer some suggestions as maybe one of them will help. Forgive me if anything seems overly obvious, as I have no idea of your technical level!

Did you manually configure and set up the other laptops that work fine?

Still... since you are using wireless, are you 100% sure the laptop is not connecting and grabbing an IP from a different router in a nearby area? That would explain most of those symptoms, if this was the case!

Can the laptop access the internet or anything at all once it has connected to the router? Does the router see the laptop?

If you are sure it is none of the above... perhaps ya should wipe the realtek drivers, uninstall the wireless device, then reinstall the latest realtek drivers to try and clear out anything...
 
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Thanks for the replies... really appreciate it.

TrainableMan .. we use Endpoint.. and I have tried with disabling it completely as well.. same issue remains.

Kougar .. I consider myself pretty good at networking issues but thanks for the pointers.

The other laptops are all auto.. IE: on DHCP. same as this one.
The IP is correct as I see the lease on the router to the laptop mac address.. I even put in static entry. which the laptop gets... but still it doesnt ping anything besides its own ip.. which ofcourse means TCP/IP is good.

For internet, we have a separate subnet setup.. and funny thing, the laptop can connect to internet on that subnet.. but that is also random, uneven.. at one time it will, at other times, it doesnt.

I also tried to remove the wireless card and re-seat in the slots, and still same..
but the card is fine as it can connect to home wireless networks.
This laptop did connect correctly before, and I do not recall making any changes that would cause this, other than adding a new user on the laptop. and users dont have admin rights to make changes either..

This one has stumped me.. lol..

I truly appreciate all the assistance. :)
 

TrainableMan

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I'm not a network guy, wish I was: $$$, so these are just things I found searching or ideas that popped into my head; not sure if they will help at all.

If it works sometimes and not others then maybe it is set up to ignore repeated requests as some sort of flood protection?

Have you tried a different cable &/or router port, maybe hardware issue?

From DOS prompt:
ipconfig /release
ipconfig /renew
Then check for a message in the event viewer corresponding to your problem.
(this was for server 2000 but I assume it still works W7 and may give you a message you can search on for ideas)

Another suggested lowering the encryption level helped them connect ...
Control Panel...Network and Internet...Network and Sharing Center...Advanced sharing settings...Under Domain in File Sharing Connections change from 128bit to 40-56bit encryption.
 
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TrainableMan.. some good points u have.

I am going to try these... and let you know.
thnx
 
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Well.. still having the same issue.

i dont see any packets from the laptop being dropped on the router as flood protection. so the router is getting the ping requests, but on the laptop.. no responses.

Another interesting thing, when I ping the laptop from another computer.. i get replies. where as any ping from the laptop itself is "destination host unreachable"

I also checked DNS server.. and everything points correctly.
The event viewer shows that browser server, DNS server, DomainController, etc were not available... which ofcourse is because the laptop cannot get responses from gateway.

changing the encryption setting also didnt help. :(

This is like finding needle in a haystack blindfolded... I will find it... just the matter of time.. :)
 

TrainableMan

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Is the laptop connected by ethernet or wireless to the router?

And you mentioned it is on a different subnet so that it has internet access. Are the other laptops that do work on that same internet subnet too?
 
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It is on wireless, the ethernet is working fine no problems at all.

and yes.. other laptops work like charm on both the subnets.

Basically we have a subnet (subnet2) for eternal users to connect to internet.. like people who come in for conference..and who dont have domain id..

whenever we connect to the main network (subnet1) everyone is authenticated with Domain. and have access to internet and other internal resources.

This laptop is the weirdest.

I have found something new.. and probably is the issue..

we have 6 different access points, and i tried to connect to a different one and i had the same issue. it connected for a few secs.. and then doesnt ping any more. so it seems there is something on the firewall/access point config that is causing this issue...

still trying.. :( lol 4th day on this issue..!

Thanks Trainableman
 

Kougar

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Another interesting thing, when I ping the laptop from another computer.. i get replies. where as any ping from the laptop itself is "destination host unreachable"
Okay, this really does make it sound like a hardware failure. My best guess is something with the receiving hardware is only intermittently working... unless I missed something you've mentioned it can send, but it doesn't seem able to receive packets.

Just for fun, I'd suggest you boot the laptop to a liveCD, any distro. See if that OS is able to work properly before or after ya configure the NIC... if it is not, then it's a safe bet something with the NIC hardware went bad. A quick swap of the NIC card will confirm it.
 
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Kougar.. i thought hardware could be an issue, but funny thing the wireless works well outside on any other network.like the home network for the user who uses the laptop.

So far I have not been able to find any settings on the routers and the access points that could have caused this.
One thing i did notice, that under advanced options for card properties through Wireless network properties.. i do not have options to select diff frequencies to test, and neither I can see any power level options.
This i think is based on driver, but i have teh latest driver.. dated Aug 2011.

sigh.. I think i might have to get an extenal usb wireless adapter to test other things.
 
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I have had the exact same problem a couple of years ago, unfortunately I can not remember what I did. Let me clean some of the cobwebs out of the back recesses of my mind, and see if I can remember. It ended up being something really simple, I remember that much.
 

Kougar

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Skydiver, sorry I missed where you had said that it worked elsewhere.

That pretty much only leaves the driver... it's certainly possible some remnant of a different or original driver is being used with the driver you are installing, so if you can nuke the wireless drivers entirely from the system you may get it working properly with a fresh reinstall of them.

I'm not personally aware of any driver cleaner programs specifically for wireless drivers so I can't recommend one, but it used to be a large enough problem that programs like Driver Sweeper had to be part of any enthusiast's toolkit for years. Latest versions work with Reltek drivers, but I don't know if it will do wireless drivers...
 
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Thanks Kougar.

Actually it is not a driver issue. After a long time spent on it.. I still dont understand how it happens, but appears to be the frequency setting on the laptop.
I tried enabling a different frequency on the WAPs which actually worked.
I also have tried different versions of the driver and none give me the option to change or tweak the frequency..
So it is kind of a hardware issue.. probably a new card will work. but it truly is strange that it was working fine before.

oh well for now, that laptop is using a separate PCMCIA card we have lying around in the office and at home the use is good too.

I really appreciate the input and support from everyone.. Thank you all!
:)
 
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TrainableMan

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Some wireless routers support multiple frequencies but not all of those support multiple frequencies at the same time. On a router that doesn't support concurrent frequencies if one user is connected at 2.4GHz then no one can connect at 5Ghz until the 2.4GHz connection is dropped and visa versa.
 
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