# Suddenly slow Windows File Sharing on Closed Network

I'm here just to get ideas. We have two PC's running XP SP2 sharing their C drives (I know this is a security risk, but its a closed network with proprietary software). They are on a closed network with static IPs. From "My Network Places" I see "C on ComputerA" on ComputerB and vice versa. When I double click them, it locks up explorer - both machines are having this issue -- which causes the proprietary software to have issues. Ping times are relatively quick, chkdsk returned no errors. Any answers appreciated!

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How to large PINGs look between the machines? Say, 5000 bytes? Try a "PING ComputerA -l 50000 -t" from ComputerB. In the last couple years, I've seen more than a few little cheapie Ethernet switches go crazy start spewing out crap traffic causing the kind of thing you're seeing. 63 byte PINGs look fine, but larger ones that require fragmentation get crazy high latency (hundreds of ms). Do the lights on the Ethernet switch look normal? –  Evan Anderson Jun 25 '09 at 17:51
You were spot on!!! Please add this as answer! –  Daniel A. White Jun 25 '09 at 18:18

## 5 Answers

Verify:

• DNS Resolution if connecting via hostname rather than IP
• Firewalls are disabled on both machines, or allow File Sharing ports (UDP and TCP 135-139, 445)
• Results from command line: net view \\PCNAME
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How about trying to connect through the administrative share at (from windows>run):

\\serverip\C\$\


Does this also crash explorer?

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Along the lines of Dave Drager, another issue could be the network cards themselves. Just had an issue with a Broadcom NIC causing connection drops when trying to RDP. I had to disable the 'IPv4 Large Send Offload' property of the NIC.

After that, all the problems with communication between that computer and any others went away...

-JFV

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Couple of ideas:

1. Add an lmhosts or hosts entry (c:\windows\system32\drivers\etc) to expedite name resolution
2. Authentication might be slowing down the responsiveness. Make sure you dupe the usernames and passwords on both systems. Or make sure you save credentials
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Based on Evan's comment, it was the network switch.

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