Why am I unable to access some https sites?

Question

Scenario:

• There are 2 laptops (HA and HB) running on Windows 8.1, both access the internet and are connected to the same wifi router (RA).Both laptops share the same DNS settings.
• Laptop HB also has a small router (RB) connected to it sharing internet to a smartphone and other portable gadgets.

Problem:

• Laptop HA tries to access some https sites (e.g. instagram) but the connection constantly times out.
• However, it is possible to access other https sites (e.g. gmail) without a problem and some do not load all the page contents

Conundrum:

• When Laptop HA connects to router RB (the one sharing laptop HB's internet) there is absolutely no problem with any connection and all pages load normally. So the question is, what could be the problem with laptop HA??

Attempted Solutions:

• flushing the DNS cache
• cleared my cache
• checked the system date and time but they are also correct
• tried changing my DNS servers to 8.8.8.8 and 8.8.8.4
• restarted the laptop after each attempt of each solution
• tried loading the site in opera, iexplore and waterfox but faced the same problem

Any alternative solutions to this problem are welcome. Hope ya'll can help me out :)

Answer 1

I've seen path MTU problems cause symptoms like this. Try this: Connect HA to RA and reproduce the problem. Now adjust HA's MTU to something low like 1300 and see if the problems go away. If they do, increase HA's MTU until you find the highest value that still works.

If your Internet connection uses PPPoE, your MTU probably needs to be no larger than 1492. If you're doing VLANs over hardware that doesn't have native hardware support for VLANs, then your MTU probably needs to be no larger than 1496.

Google sites avoid MTU problems by always negotiating a TCP MSS (Maximum Segment Size; the TCP-level equivalent of an IP MTU) of something like 1380. Most other sites use the typical Ethernet MTU of 1500, so if you've got a hop on your route that can't handle that MTU and doesn't handle fragmentation and ICMP fragmentation notifications properly, most sites will hang or only partially load, but Google sites will work fine.