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The VPN connects successfully but after some time the connection is unusable (VPN is used as primary gateway). Ping would reveal:

ping: sendto: No buffer space available

This looks like the same issue discussed here:

Hopefully you might have a workaround.

I have Mac OS X 10.6.4

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I have this issue too. Unfortunately the vpn is a commercial vpn so I can't try the suggestions listed below (I don't know of any hosts on the network). – fuzzyman May 16 '11 at 10:37

I can confirm that sending constant pings to a host on the VPN will help overcome this exact issue.

Find an ip address of a computer on the network you know will be happy to take a pings all day (a web server maybe?). Open a terminal by going into spotlight (command+space) and typing 'Terminal'. In the window that appears type (without quotes)

ping "ip-address-here"

so for example:


Then just let it ping for as long as you need to keep your session open. I've found that leaving it all day has no negative affects.

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I found out that the issue is most likely a UDP session timeout in my router (decreased from 120 to 90). And I have to send constant pings to a remote node (in the VPN remote network).

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