vpn issues

i have vpn setup on several small business 2003 servers. all work great.

all of a sudden one client can't copy/paste large files from server to laptop across vpn. works fine from any other pc. when i try to paste a 2mb file, i get "the specified netowrk name is no longer available"...and the remote windows from the server files closes automatically.

i have scoured the internet for a fix and ran system restore to no avail. i am trying to avoid a reformatt. can anyone help?
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Rob WilliamsConnect With a Mentor Commented:
Sounds like some temporary degradation in the connections. Perhaps your ISP had reduced performance for some reason ,or is it possible someone at one end of the tunnel or the other was affecting performance by downloading large files, such as music files, or listening to streaming media? Should it happen again try the MTU adjustments. Often a lower grade connection can have improved stability with a lower MTU.
Hopefully it was a 1 time occasion.
Thanks for the update.
Rob WilliamsCommented:
Can the laptop resolve the corporate domain name when connected?  run from a command line:
nslookup  mydomain.com
then try the same for the server to which they are connecting
nslookup  myserver
If not it may be a DNS issue. Check that only your DNS server is listed as a DNS server in the users   ipconfig  /all  results   If the computer is not a member of the domain add the domain suffix such as  mydomain.local  to the DNS tab of the users network adapter, in DNS suffix for this connection, to see if it helps.
what kind of file do you try to copy?
i know it kind of weird question but i have my reason to ask....
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mehrdadalaeiAuthor Commented:
yes, dns resolves fine. i can see all shared folders and can copy and past or even eopne small pdf, word, exel files.....i can't open or copy files over 1mb in size.

same for email...outlook connection to exchange over vpn cannot download attachments over 1mb. i don't want to troubleshoot outlook/exchange because i know the issue revlves around a slow vpn connection or some kind of packet size limit.

Rob WilliamsCommented:
I would try adjusting the MTU (Maximum packet Transmission Unit) packet size on both routers and computers. If the MTU is set too high for your connection it can cause browsing, file transfer, and dropped connection, issues. The routers usually have a box to set manually, and the easiest way to change on the computers is to use the free DrTCP tool from:
The default is 1500, try dropping to 1300. If performance improves gradually increase to 1500. There are ways to test for the optimum size of the MTU such as:
However, this is not accurate over a VPN due to additional overhead. The best bet is to set it to 1300, and if it improves the situation, gradually increase it to a a maximum of 1430.
A couple of related links:

mehrdadalaeiAuthor Commented:
thank you rob,

i was going to try these as i found this exact info yesterday but the problem fixed itself. very odd, now i can copy large files over vpn without issue. maybe a windows update fixed it....not sure.

mehrdadalaeiAuthor Commented:

would you have any idea as to why something would change to cause the issue in the first place?
mehrdadalaeiAuthor Commented:
thanks. it was odd because the issue was there for 8 days and then went away. i can rule out all of your possibilities except isp reduced performance.

Rob WilliamsCommented:
Thanks mehrdadalaei .
ISP's can be up and down a bit, but I was surprised when you said 8 days. Usually 48 hours at the most, not to say it isn't possible. I hate those problems that resolve themselves. You are always concerned you have a time bomb ticking away. I guess time will tell. Good luck with it.
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