If a connection is using Split DNS, however no DNS domains have been set, Viscosity will add a "WARNING: Split DNS is being used however no DNS domains are present. The DNS server/s for this connection may not be used." warning to the log.

About the Warning

When Split DNS is used, DNS requests for VPN specific domains will only use your VPN connection's DNS servers. Viscosity will automatically use Split DNS mode when connecting to a VPN connection with a split-traffic setup (only some traffic is routed through the VPN connection).

With Split DNS you can specify that DNS requests for "anything.example.com" should use your VPN's DNS servers by setting a DNS domain of "example.com". Likewise, DNS domains also act as search domains, allowing you to just type "anything" into your web browser to access the same server as well. DNS requests for all other domains will use your computer's normal DNS servers.

If Split DNS is set for a connection, however no domains are associated with it, then the VPN DNS servers will essentially go unused. If the above warning is appearing in the log, then this is the case.

Resolving the Warning

There are two ways to resolve this issue:

Recommended Method: Add one or more DNS domains to the VPN connection in Viscosity (or push these from the VPN server). For example, if you're connecting to your workplace, you may want to add your workplace's web domain (e.g. "workplace.com") as a DNS domain. For information on adding DNS domains to a connection please see Configuring DNS and WINS settings.

Alternative Method: An alternative to using Split DNS is to use Full DNS. This will result in all DNS requests using your VPN DNS servers, not just those associated with the VPN connection. Please be aware that this may result in non-VPN network access to fail if the VPN DNS servers are not configured to handle all DNS requests. For information on changing the DNS mode to Full DNS for a connection please see Configuring DNS and WINS settings.

About Other VPN Clients

Most other VPN clients do not have Viscosity's powerful Split DNS support. These clients instead always use the VPN connection's DNS servers for all DNS lookups on your computer, even when using a split-traffic setup. This may make it seem like DNS requests with these clients "work" when they don't work in Viscosity (which will instead display the warning in this article). However, they are in-fact leaking all DNS lookups through the VPN connection, which can have important security and privacy implications.

If you simply want Viscosity to replicate the functionality of these other clients, you can follow the "Alternative Method" method instructions above. However, we recommend making proper use of Viscosity's Split DNS support instead.