Viscosity performs a "reachability check" before attempting to connect a VPN connection, or whenever a network change is detected. This check allows Viscosity to determine whether the remote VPN server can be reached over the network so the connection can be established. This check is also performed whenever your computer's network connection changes (e.g. you change wireless networks) to ensure that the VPN server can still be reached.

If a reachability check for a connection fails, Viscosity will abort the connection attempt and display the "Connection Name Could Not Be Connected Message" alert.

A reachability check may fail for a number of reasons:

• Your computer isn't connected to a network. Check that your computer is correctly connected to your wired or wireless network. Try reconnecting to the network if you are unsure.

• Your computer doesn't have a valid network connection. Check that you can access other resources over your network, such as websites, to test your connection. Some pubic wireless and hotel networks may require you to open a page in your web browser before you can access the internet.

• The address for the remote VPN server is incorrect. Edit your connection and make sure the address is correct, or contact your VPN Provider to ensure your connections are valid and up-to-date.

• Viscosity could not resolve the address of the VPN server. Viscosity uses your computer's DNS servers to resolve a VPN server's domain address (e.g. myvpnserver.com) into an IP address it can connect to. If your computer's DNS servers are invalid, or they can not be reached, Viscosity will be unable to establish a connection. Check that your computer's DNS settings are valid. Alternatively you could try using Google's public DNS servers, or OpenDNS's servers.

• Viscosity could not find a valid network route to the VPN server. Viscosity checks your computer's internal network routing table to determine whether there is a network path to the remote VPN server. If there is no route that allows a connection the reachability check will fail. Check that there is no software installed, or other VPN connections active, that could interfere with your computer's routing table. Try restarting your computer to flush the routing table. If the reachability check only fails after your VPN connection has disconnected, see the Losing Network Connectivity Once Disconnected article.