We just moved last week from Apache to Nginx as web server for piwik and since then every IP addreses gets displayed with ::ffff: in front of it (for example: ::ffff:192.168.10.20). I guess this the IPv6 representation but we would like to avoid this and get the normal IP address back as our excluding doesn’t work anymore.
Thanks, I have now followed your advice and modified the listen parameter on my nginx configuration in order to avoid this annoying ipv6 formatting and having to modify all my excludes.