Because the Cisco VPN client is not working properly on Windows 8.1, we had to use Cisco AnyConnect Client.

Here begins a nightmare that lasted for several days.

After the AnyConnect client connects to a remote computer all local TCP connections are interrupted.

If your computer has initiated an application that for example communicates with the database, it loses the connection to the database and must be restarted.

It took several days to find a reason why this is happening:

VPN connection that is established does not allow the IPv6 protocol, and all of local TCP connections that have been established over IPv6 protocol were terminated.

Therefore, the solution is very simple:

disable IPv6 protocol on the local network adapter or in the connection to the database use a fixed IPv4 address (n.n.n.n) instead of the computer name

This will force connection to use IPv4 protocol.