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Known Issues

PLEASE discuss any problems on the Tunnelblick Discussion List.

The following are known problems or limitations in Tunnelblick:

  • The standard script that "Set nameserver" uses handles DNS for most common setups. For other situations, one of the other settings may work, or you can use custom scripts. See Setting up Configurations for details.

  • When attempting to connect to a VPN using a TAP connection, OpenVPN may display a series of "write to TUN/TAP : Input/output error (code=5)" error messages. Although a few of these messages are normal, if they continue to be displayed for more than a few seconds, try to connect using "Set nameserver (alternate 1)".

  • If "Set nameserver" is selected, all "up" and "down" options in the OpenVPN configuration file will be ignored. To work around this, include appropriate parts of the standard up/down scripts in your own scripts and select "Do not set nameserver". (The reason for this is that OpenVPN's "down-pre" option cannot be used with the standard "Set nameserver" down script, but may be used by custom scripts, so the two scripts cannot be used together.)

  • High values for the OpenVPN "verb" option may cause high (99+ %) CPU use by Tunnelblick. Reduce the "verb" value in the OpenVPN configuration file to 3 or 4 for best performance.

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