High Quality Content by WIKIPEDIA articles! AICCU (Automatic IPv6 Connectivity Client Utility) is a popular cross-platform utility for automatically configuring an IPv6 tunnel. It is free software available under a BSD license. The utility is originally provided for the SixXS Tunnel Broker but it can also be used by a variety of other tunnel brokers. The utility is originally provided for the SixXS Tunnel Broker but it can also be used by a variety of other tunnel brokers.