I have a Fedora Linux box which I am using for a captive portal. Basically this is the setup, I have 3 vlans whose gateways are assigned to eth0.91, eth0.93 and eth0.90. The traffic is checked by iptables and if the MAC address of client is in iptables then the traffic if forwarded out.
All Windows OS machines can access all sites with no problems.
Linux machines will have inconsistent problems with https sites. Some https sites won't load at all, others just authentication problems. I used Wireshark at the point of authentication and the client machine will try to transmit the same packet 5-6 times, with no reply from the https site. After these 5-6 tries, the https site will send a RST, ACK packet back to the Linux system. Then the page will time out. But I can reload the https site again with no problems, but still cannot authenticate. HTTP, ping, tracert all work, all the time.
What is the difference here between the Linux OS and Windows OS that would treat https packets differently?