Avira Antivir is using both IPv6 and IPv4 protocols to update the virus signature files. But after installation of ZAAV9, I never got Avira updated successfully.
It kept reporting errors like following when updating.
[UPD] [INFO] Downloading of 'http://[2a01:138:a001:201::21]/update/idx/master.idx' to 'C:\Documents and Settings\All Users\Application Data\Avira\AntiVir Desktop\TEMP\UPDATE\idx\master.idx'.
[UPDLIB] [ERROR] Download manager: An error occurred inside the WinINet library.