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Strange LAN connection issue

Last response: in Networking
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October 4, 2010 10:14:53 PM

As always networking is being a real pain...

I have 3 devices on the network, a desktop, a laptop and a switch.

Both my laptop and desktop can access the internet (ipv4 only) through the LAN, and other devices on the network(both ipv4 and ipv6 ones). However they wont talk to each other :( 

The desktop can see the laptop (it shows up in the "Network" window, and "ping mylaptop" gets an address), however connecting in any form fails (no response). The laptop can not see the desktop at all, doesnt even find an address for the "ping mydesktop" (I even tried an explicit ping xxx.yyy.zzz.www but no response).


Desktop: Windows 7 64bit Home Premium
Laptop: Windows Vista 32bit Home Premium



This is really bugging me. I have gone through all the settings and can not see why just my 2 devices would refuse to communicate in this way...



Network Diagram (not complete by any means, and most likely misses a lot of intermediate devices/layers especially in getting to the internet)
  1. Desktop Laptop Freewire Phone
  2. | | |
  3. |gigabit LAN| |
  4. | | |
  5. | | |
  6. gigabit ethernet switch
  7. |
  8. | |-----other
  9. organisations network-----peoples
  10. (100mbit) |-----devices
  11. |
  12. |
  13. |
  14. internet
a b D Laptop
October 5, 2010 5:35:36 AM

have you tried disabling the firewall on the three computers, setup the shares, and then enable the firewalls again?
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October 5, 2010 7:45:26 AM

To throw more strangeness into this problem this morning my laptop decided to "see" the desktop but attempting to connect to the desktop failed while the desktop was able to access the laptop fine.

I forgot about personal firewalls... Disabling the McAfee firewall on both got it to work, however I still dont see what the firewall is doing to break this between just these two devices and since this is not a fully secure network (can a network with several hundred people having access rights and ethernet connectors in nearly every room ever really be all that secure?) I don't really want to leave the firewalls off.
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a c 206 D Laptop
October 5, 2010 6:22:47 PM

It does not matter how your network is, it only matters what the firewall does. The firewall does not care or see how your network is setup or where you are located. The Firewall's job is to prevent access that it thinks should not be happening, and unless you tell it what is OK and what is not OK, it will just block things.

Computer software and hardware is not smart. If you place your monitor on the floor, it won't tilt itself up so you can see it or move aside so you don't hit it with your feet. The software also can't tell if you are on a secure network or in the middle of Times Square handing your computer to strangers.

You can go through the settings and allow access from certain locations in the firewall.
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October 5, 2010 10:05:00 PM

Well as I said I see no reason why the firewall is blocking this exact connection case when all other connections are fine. There is nothing set to explicitly allow/disallow the devices in question to communicate, and both devices connected fine to each other on a different network...
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