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Unit not detecting other devices on network - Windows 7

Posted on 2010-09-08
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Last Modified: 2012-08-13
We provide support for a small business that only uses 4 pc's. Normally they all connect to the same network and can detect and share files without issue.
However, they've contacted us to report that 'recently' (nice and vague... could be anything between 1-4 weeks since they noticed issues) one of the computers ( a laptop used both in the office and at home) has stopped being able to detect any devices on the network. They're connecting via a public network and the other machines can still detect the offending unit without any problems.

It's using windows 7 (entire office is w7 or vista), LLTD protocol is enabled, as is network discovery. It can ping the other devices on the network, I can map a network drive and get the files, but it will not detect other devices in the network and sharing center and cannot sync files as it claims network is disconnected.

This has me thoroughly confused now and any advice would be appreciated

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Question by:Sinkingnotswimming
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by:SHIELD1
ID: 33628404
I have noticed a similar problem with windows 7 machines that connect via a wireless connection and it may just be a matter of slow DNS over non-hard wired connections.  Isually once logon scripts have run including drive mappings then network items start popping up.  It may be worth giving them a flushdns/registerdns script or batch file just to speed things up?

Just a thought
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by:Sinkingnotswimming
ID: 33644247
Nice thought, but unfortunately this is happening well after logon scripts have completed.

It would appear to be some kind of firewall issue. Although when checking the GUI both inbound and outbound conections seem to be st up correctly, when the firewall gets turned off the unit will sync with the other computers on the network (though it still doesn't detect them in the network places)

What confuses me is that if I manually enter the network path to another computer, it can connect and the other unit THEN shows up in the network computers. I can also map a network drive to the other unit even if it's not showing up as part of the network.

As an additioonal query... why when the firewall is turned off can it now sync, but still not detect other computers on the network... am I missing something obvious (have this horrible feeling that I can't see the woods for trees)
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SHIELD1 earned 500 total points
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having the firewall off may indicate that one of the ICMP rules enabled by default in the windows firewall is blocking sync or indeed just standard firewall rules is blocking it - which reminds me, is file and printer sharing enabled as "allow" in the firewall rules and is it allowed/enabled in the network card properties?  Also check the server NIC.

The fact that you can map to the resources manually suggests that DNS is working fine it may just be a case of network discovery & active directory, and/or global catalogue on the server being slow.

It may be worth looking at the event log for active directory errors, DNS errors, group policy errors?  These normally indicate more subtle DNS errors.  In which case you can run the freely available DNS & AD diagnostic tools.

In the network browsing do your clients find that other PCs on the network show up before any other network resources?  That may indicate browser master conflicts.  It may be worth installing and running netshark just to analyse the network traffic.

My last thought is putting main DNS server IP address as primary DNS for clients (if that's not the case already) either manually or in DHCP and check your event logs and DHCP management console for IP address conflicts.  Ping the server from one of the clinets ping -a servername and just see how long the server takes to repsond and whether it reolves the name to an IP address corectly.

Sorry to leave this so long!
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by:SHIELD1
ID: 33793836
hiya thanks for awarding me this solution I hope I was able to help and not just that you decided to close due to lack of feedback?  If you are still stuck please submit additional info otherwise take care :)
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