Cisco SecureClient (AnyConnect), macOS, DNS, and IPv6

So you don’t have native IPv6 but now you have IPv6 via your VPN and DNS/connections just won’t work?

Welcome to a macOS feature that’s been around since 2018 to ignore IPv6 if your primary interface doesn’t support it.

While this was fixed for a bit in macOS 13.4 it came back.

Run BEFORE you connect to the VPN:

sudo scutil --disable-service-coupling on

Related Tunnelblick issue: https://github.com/Tunnelblick/Tunnelblick/issues/490#issuecomment-447085756