If you are a network engineer in this day and age, then you are probably familiar with and regularly using IPv6 (at least on your home lab network). I personally run my home network dual-stacked and have been recently annoyed by how VPN clients (mostly Cisco AnyConnect) handle dual-stacked clients. I have found that when left unconfigured (using defaults), AnyConnect likes to dump all IPv6 traffic silently on dual-stacked clients. This causes IPv6 enabled public websites and services (just the unpopular ones…like Google, YouTube, Facebook, etc) to hang while trying to connect using the looked up AAAA DNS record.
Here are a few tricks I have found to configure AnyConnect to properly handle dual-stacked clients to keep those eyeballs happy. The IPv6 must flow!