the configuration for IPv6 part:
FastCGIserver {
    FastCGIid = PHP5
    ServerRoot = /usr/local/var/www/hiawatha/webui
    ConnectTo = 127.0.0.1:2008
    Extension = php5
}
VirtualHost {
    RequiredBinding = IPv6_80
    Hostname =  2000:1977:0:61:219:77ff:fe44:9f40
    WebsiteRoot = /usr/local/var/www/hiawatha/webui
    StartFile = index.php5
    UseFastCGI = PHP5
    ExecuteCGI = yes
}
the following is the log of access the default page of IPv6 host, IPv6 network is OK:
2014-07-28 07:23:40 info    hiawatha: binding->poll_data->revents != 0, binding_id=IPv6_80
2014-07-28 07:23:40 info    hiawatha: accept connection, binding_id=IPv6_80
2014-07-28 07:23:40 info    hiawatha: binding->interface.family == AF_INET6
2014-07-28 07:23:40 info    hiawatha: fcgi_server_match.....
2014-07-28 07:23:40 info    hiawatha: fcgi_server_match, fastcgi->size=0 extension=php5
2014-07-28 07:23:40 info    hiawatha: session->cgi_type=3
The session->host->fast_cgi.size is 0 makes me puzzled. What's your idea about this? Is my configuration wrong? 
thanks.
- Damien
Hiawatha version:  9.6
Operating System: Linux OS