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We're having a very odd issue with two servers communicating with each other over UNC paths. We have four web servers total all hooked up to the same switch, running the same OS version, patch level etc. Two of the servers cannot access each other through UNC shares, but have no issues accessing the other two servers. We've ruled out the switch and cabling, and at this point have run out of ideas.

When we try to connect via UNC (i.e \ip\c$), the System process goes to 50% and is effectively hung. You pretty much have to reboot the box.

OS: Windows 2003 Web Edition, Service Pack 2 NIC: Broadcom NetExtreme

Anyone care to take a shot?

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You can probably find out a lot about what's going on if you use MS Network Monitor\Wireshark to see if there's any odd traffic going on at the same time. – Helvick Feb 24 '10 at 22:36
A little more detail would help. When you say that they can't access each other, what specifically happens? Do you get a "network name not found" message or an "aacess denied" message, or something else? Have you tried using the names and ip addresses? – joeqwerty Feb 25 '10 at 3:50

Throwing out some haymakers:

  • Rebuild the TCP/IP stack
  • Install a WINS server
  • Disable TCP/IP offloading on the NICs (Microsoft Support told me once that Windows doesn't do well with offloading)
  • Make sure the speeds are the same for each network card and switch port (preferrably all set at 1Gb)
  • Start in Safe Mode with Networking on one and see if it can access the other. Then try both in SMwN and see what happens. At least you could narrow services down that way.
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Just to throw in a few more things..

  • Can you ping problem machines from non-problem machines, and vice versa
  • Is your DNS OK? Smells like a DNS issue to me (especially if the ping doesn't work)
  • Try "ipconfig /flushdns" for good measures
  • Are the networking drivers Broadcom ones or Microsoft generic ones? If Broadcom ones, are they all the same driver version across all servers? It might also be worth checking if a newer driver is available from Broadcom.
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Ping is no problem, dns is setup correctly. I'm trying a rebuild of the IP stack as we speak. – user35954 Feb 26 '10 at 13:04

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