I'm trying to use TeamViewer but have a problem when trying to access the network with IPv6 via GSM.
Can I somehow turn off IPv6 and use only IPv4? I am using an iPhone 6 Plus with iOS 8.3.
In general, no. Many mobile carriers are deploying and Apple is supporting IPv6 only networking. You may still get an IPv4 address in some cases, but that space is about exhausted in many regions and you’ll want to reach out to team viewer support or your IT professional if you have one for assistance configuring a proper IPv4 to IPv6 gateway or look for a screen sharing solution that’s compatible with this new technology that was proposed in 1992 and became a draft standard in 1998 and defualt standard in 2017.
In short, IPv6 is designed for mobile in that thousands of devices per person can now have a unique address and this has significant security and performance benefits over IPv4. Turning off IPv6 in 2018 will break many people’s mobile data, but check with your carrier to be sure. By removing the NAT layer, each device can have the proper firewall and access rules and not all be lumped behind a shared address. It also enables better VPN capabilities if you indeed want to hide the source address and can now have your r served addresses at home and away.