Site to site tunnel file sharing problem

Also Posted On Cisco Group:

Hello!

I have 2 Cisco 2801 series routers (one at our corporate office, and
one at our branch location). I have setup a site to site vpn over an
IPSec tunnel. The tunnel works perfectly fine in most ways. I can
ping any address from either location at the other location. I can
browse to any share on any computer. I can copy files that are
approx. 3KB or smaller to PCs at the other location. I CANNOT,
however, copy files larger than approx. 3KB. I get an error message
after about 30 seconds that says "Cannot copy (name of file): The
specified network name is no longer available." I can then take that
exact file, remove enough information from it to take it below approx.
3KB, copy the file again, and it finishes in no time flat. I am sure
this is a result of the MTU fragmentation.

Oh, the best part: This only happens on some computers. From certain
computers, it doesn't matter what the size of the file being copied,
it works perfect, other computers, it is extremely consistant. I have
found a way to, on a PC by PC basis, resolve this issue (but would
like a blanket resolution)...here's the resolution to fix one PC at a
time: open regedit, navigate to HKEY_LOCAL_MACHINE\System
\CurrentControlSet\Services\Tcpip\Parameters and create a new DWORD
called EnablePMTUDiscovery and set the value to 0. Restart.

Is there a way to get this same result by making a change to the
router. I have tried these two things with no avail:

Router# config t
Router(config)# int tunnel0
Router(config-if)# ip mtu 600

&

Router(config-if)# ip tcp adjust-mss 600

Any Ideas?!?!?!? Thanks guys!

It could be the MTU issue. these search results may help,

network name is not longer available
But when I try to copy a file from my PC to the Server, it hangs for a minute and then returns "The Network name is no longer available" (we're talking 1mb ...
http://www.chicagotech.net/Q&A/vpn17.htm - Similar pages

specified network name is not longer available
System error 64 - The specified network name is no longer available. System error 53. The network path was not found. Event ID 3013 - Description: The ...
http://www.chicagotech.net/troublesh...temerror64.htm - Similar pages

vpn drop connection
Also, you may receive "The Network name is no longer available" message when you try to copy a file from the VPN client to the Server. ....
http://www.chicagotech.net/vpnissues/vpndorp1.htm


Bob Lin, MS-MVP, MCSE & CNE
Networking, Internet, Routing, VPN Troubleshooting on http://www.ChicagoTech.net
How to Setup Windows, Network, VPN & Remote Access on http://www.HowToNetworking.com
"Robert Jacobs" <(E-Mail Removed)> wrote in message news:(E-Mail Removed) oups.com...
Also Posted On Cisco Group:

Hello!

I have 2 Cisco 2801 series routers (one at our corporate office, and
one at our branch location). I have setup a site to site vpn over an
IPSec tunnel. The tunnel works perfectly fine in most ways. I can
ping any address from either location at the other location. I can
browse to any share on any computer. I can copy files that are
approx. 3KB or smaller to PCs at the other location. I CANNOT,
however, copy files larger than approx. 3KB. I get an error message
after about 30 seconds that says "Cannot copy (name of file): The
specified network name is no longer available." I can then take that
exact file, remove enough information from it to take it below approx.
3KB, copy the file again, and it finishes in no time flat. I am sure
this is a result of the MTU fragmentation.

Oh, the best part: This only happens on some computers. From certain
computers, it doesn't matter what the size of the file being copied,
it works perfect, other computers, it is extremely consistant. I have
found a way to, on a PC by PC basis, resolve this issue (but would
like a blanket resolution)...here's the resolution to fix one PC at a
time: open regedit, navigate to HKEY_LOCAL_MACHINE\System
\CurrentControlSet\Services\Tcpip\Parameters and create a new DWORD
called EnablePMTUDiscovery and set the value to 0. Restart.

Is there a way to get this same result by making a change to the
router. I have tried these two things with no avail:

Router# config t
Router(config)# int tunnel0
Router(config-if)# ip mtu 600

&

Router(config-if)# ip tcp adjust-mss 600

Any Ideas?!?!?!? Thanks guys!

Robert,

Thank you for your response. I will try using your "How to modify the
MTU Settings for VPN Connections on XP" for a separate issue I am
experiencing. However, I as stated in my OP, I was wondering if there
was a way to make this type of change (since it is a site to site VPN)
on the router's interface (Tunnel0) on each router? I know that
setting the EnablePMTUDiscovery value to 0 on a PC by PC basis will
fix our problems, but I don't want to have to do this on every
computer, and then remember to do this on every machine we distribute
in the future. I would like a blanket way of resolving this issue.
Also in my OP I mentioned that I did try adjusting the ip mtu and the
ip tcp mss with no avail. Is there a setting at the router level that
will have the same effect as disabling PMTUD on each machine?

Thanks for your help!
The other Robert

I thought you might fix this issue by modifying the MTU on the router instead of going to each workstation. If you do want to do that in each computer, I believe you can export the registry and run it from the logon script.

Bob Lin, MS-MVP, MCSE & CNE
Networking, Internet, Routing, VPN Troubleshooting on http://www.ChicagoTech.net
How to Setup Windows, Network, VPN & Remote Access on http://www.HowToNetworking.com
"Robert Jacobs" <(E-Mail Removed)> wrote in message news:(E-Mail Removed) oups.com...
Robert,

Thank you for your response. I will try using your "How to modify the
MTU Settings for VPN Connections on XP" for a separate issue I am
experiencing. However, I as stated in my OP, I was wondering if there
was a way to make this type of change (since it is a site to site VPN)
on the router's interface (Tunnel0) on each router? I know that
setting the EnablePMTUDiscovery value to 0 on a PC by PC basis will
fix our problems, but I don't want to have to do this on every
computer, and then remember to do this on every machine we distribute
in the future. I would like a blanket way of resolving this issue.
Also in my OP I mentioned that I did try adjusting the ip mtu and the
ip tcp mss with no avail. Is there a setting at the router level that
will have the same effect as disabling PMTUD on each machine?

Thanks for your help!
The other Robert

On May 17, 4:11 pm, "Robert L [MVP - Networking]"
<nore...@hotmail.com> wrote:
> I thought you might fix this issue by modifying the MTU on the router instead of going to each workstation. If you do want to do that in each computer, I believe you can export the registry and run it from the logon script.
>
> Bob Lin, MS-MVP, MCSE & CNE
> Networking, Internet, Routing, VPN Troubleshooting onhttp://www.ChicagoTech.net
> How to Setup Windows, Network, VPN & Remote Access onhttp://www.HowToNetworking.com
> "Robert Jacobs" <robertjacob...@gmail.com> wrote in messagenews:(E-Mail Removed) ooglegroups.com...
> Robert,
>
> Thank you for your response. I will try using your "How to modify the
> MTU Settings for VPN Connections on XP" for a separate issue I am
> experiencing. However, I as stated in my OP, I was wondering if there
> was a way to make this type of change (since it is a site to site VPN)
> on the router's interface (Tunnel0) on each router? I know that
> setting the EnablePMTUDiscovery value to 0 on a PC by PC basis will
> fix our problems, but I don't want to have to do this on every
> computer, and then remember to do this on every machine we distribute
> in the future. I would like a blanket way of resolving this issue.
> Also in my OP I mentioned that I did try adjusting the ip mtu and the
> ip tcp mss with no avail. Is there a setting at the router level that
> will have the same effect as disabling PMTUD on each machine?
>
> Thanks for your help!
> The other Robert

Thanks Robert,

I was hoping to not have to do that (This will probably end up being
our solution though) because I did'nt want to have to worry about this
for each computer we add to the network in the future. I did try to
change the MTU and the MSS on the router, but it had no obvious
effect. I guess I will keep a lookout.

BTW, in my earlier response regarding a separate issue I am
experiencing, it's pretty much the same problem I'm having with the
Tunnel, but it's happening on remote PCs connecting to a VPN here.
Again, it works fine on most remote machines, but other's cannot copy
files larger than approx 3KB. Making the change listed above (setting
the EnablePMTUDiscovery value to 0 on the individual PC) doesn't
resolve this (I thought it might since it seems to be the same type of
problem). Also, changing the MTU on the local machine as listed in
your "How to modify the MTU Settings for VPN Connections on XP" by
adding a TunnelMTU DWORD to the correct key and entering a decimal MTU
doesn't resolve this problem either. Do you have any idea why neither
of these settings seem to work from a remote machine, but, at least
the first change, works on local machines going over the VPN Tunnel?
I just find it very strange....

Thank you again for your help, Robert (or Bob as you listed in your
signature)

If anybody wants to know, I never found a way to make a global change
to the routers that would match the outcome of setting the
EnablePMTUDiscovery to 0 on each PC, so I just set the
EnablePMTUDiscovery to 0 on each PC via group policy.

In order to fix my "separate issue" with the external computers having
the same problem when connected via VPN to the office, I was a bit
mistaken. The problem was actually that those computers couldn't
RECEIVE files larger than 3KB, but copying files wasn't the problem.
Sooooo, I setting the EnablePMTUDiscovery to 0 on each PC
inadvertantly fixed the external VPN problems as well!!! Hope
this helps anyone running into the same or similar problem

(again, to set the EnablePMTUDiscovery to 0, go to HKEY_LOCAL_MACHINE
\System\CurrentControlSet\Services\Tcpip\Parameter s and create a new
DWORD called EnablePMTUDiscovery and set the value to 0. Restart.)