Odd firewall - LAN issue

Oh-Fudge

I don't know how many people read the PC threads on a primarily construction oriented forum, but I like this forum a lot so I'll give my computer question a try.....

For no 'apparent' reason a few weeks ago my Window$XP firewall won't let the other computers on my LAN connect to mine unless the firewall is turned completely off. Even when "sharing" is enabled.

Setup:
4 PC's
All Window$ XP Pro
Lynksys wireless router LAN

The other 3 computers can connect to each other with their firewalls on, I can connect to the other 3 computers with my firewall on. Nobody can connect to me when my firewall is on even when I allow "shared" folders. All is well when my firewall is off, but then I have no firewall .

Thoughts? Please don't tell me to buy an Apple Mac, I'm not JP Gotrocks

gregzoll

Is this just the XP firewall, or a third party software product that you are using, for "Internet Security"?

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Oh-Fudge

Window$XP factory firewall.

gregzoll

Look through the info at http://www.ezlan.net Also a lot of times, the router can have a hand in it. Also http://support.microsoft.com/kb/903267

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Oh-Fudge

Thanks Greg, I hadn't seen that "ezlan" website before. Don't know if it'll help me, but it looks like it might have some useful information!

chrisn

I am sure you know this but sometimes just unplugging the router and letting it sit for a minute fixes things( after plugging it back in!)

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gregzoll

You don't even have to let it sit for five minutes. Just unplug, count to ten then plug back in.

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Oh-Fudge

thanks Chris, well aware, my experience level is that I build my own systems from the motherboard up, and I set up my office wireless LAN. But this odd firewall issue is something that I have never encountered before.

rossfingal

Do you have some type of "Router" -
Reset the Router.
Oh - "Windows XP" firewall - get another "Firewall" -
There are very, good "free one's" available.
If you have further problems - go here -
bleepingcomputer.com
They'll help you out!

rossfingal

Oh-Fudge

thanks Ross, yes I have reset the router and done all of the basic stuff, reset the "exceptions" in the firewall, etc. I know Windoze firewall is weak, but I don't want to mess up my network any further by installing 3rd party firewalls. I tried Comodo and my network didn't work at all. And in my office work comes to a standstill without the network.

I have seen 'bleepingcomputer.com', it often has been helpful, great website.


HEY! Just noticed this is my 100th Post! Woop, woop!! (I have to get a life...)

rossfingal

If you used "Comodo" - did you turn of the built-in firewall, first?
Even if you turned off the firewall - the "Service" it's running on could
be restarted when you restart the computer.
Then you're running 2 firewalls - talk about "unpleasant" conflicts!!
Reseting the Router is not always just unplugging it.
There's ways to do a "Hard" reset with most Routers.
There is also the possibility that your Router has become "compromised-
infected"!
Consult the documentation for the Router.

Don't you Hate them "Puters" to pieces!?!!

An aside - I feel your pain!
Bought a computer back in 1998 - never touched one before -
scared I'd break it!
Built 40 to 50 since then.
What FUN!

rossfingal

rossfingal

Here's another thing to consider -
you could have an "unpleasant guest" on your computer that's
interfering with your "Security" settings.
Yes, it's been known to happen!
If your computer "faces" the Internet - the other computers see the Internet through your
Router/computer - first thing that's going to be compromised is your computer.
Also, maybe your Router.
OUCH!

RF

dougp23

Try this MS KB article:

http://support.microsoft.com/kb/298804

Somewhere in there it talks about opening ports for file sharing, if memory is correct these are NetBios ports, so lowish numbers like 135 and 137 I think, it's in the article.

See if that helps!

Oh-Fudge

Interesting Doug. In my case, if it were the wireless router blocking file sharing, wouldn't it affect all 4 computers and not just mine? And I can connect to the other computers, but they can't connect to me. Kinda' like a one-way valve. I don't know, just wondering. I have to read that about 20 more times before I understand "Micro$oft Speak". Thanks for the link!

RedHelix

My knee-jerk reaction is to say turn off the firewall. A lot of businesses disable it through group policy to avoid hassles like the one you are describing, and to just let the layer 3 firewall appliances do the work.

Reason being: A secure/PCI environment is one thing, where client-side firewalls are a great help in preventing worm propagation and stopping intruders... but on a home network, and even within 4-5 PC workgroups, I just don't see a point in bothering to set up a firewall anywhere but on the WAN interface of my router.


But if you reeeeally want to keep that firewall enabled....

I suggest you use a port-scanning tool like nMap. It is intended as a tool for testing security vulnerabilities, but also comes in handy for smoking out a misconfigured firewall.

From another PC on your network, install nMap and run a 'Regular Scan' on the problematic computer's IP address.

This scan will show you all open ports on the target PC. In this case, you want to verify port 445 (SMB) is open. If it's not listed as open, sit down at the problematic PC and verify you have allowed it on the Windows Firewall, and that Windows File Sharing is enabled. (The latter is probably already true, since you said it works when the firewall is turned off.)