New router nannying me?

[N Dentressangle]

Since going with Post Office broadband a couple of weeks ago, some websites (all harmless!) seem to be inaccessible with Chrome, Brave or Edge on my Windows 10 laptop.

The error message returned is this:

This site can’t provide a secure connectionwww.gloucesterbrewery.co.uk sent an invalid response.
Try running Windows Network Diagnostics.
ERR_SSL_PROTOCOL_ERROR

or similar. Diagnostics turns up nothing.

If I use my mobile and connect through 4G rather than the home wifi then these sites work fine.

Any ideas of what's going on please?

[OlonMusky]

Change the DNS settings on your laptop/computer to e.g. OpenDNS ones:

208.67.222.222
208.67.220.220

If it works after that then your ISP is doing some nasty st with their default DNS.

[andybebop]

I believe they turn on safeguard by default.This explains how to turn it off.

https://www.postoffice.co.uk/broadband-phone/safeg...

[jw673]

Try reducing the MTU size on your wifi adapter.

It's probably 1500 (keep a note of the current value) - try 1480 and see if that helps, if not try lower values. You can always set it back to the original value if it doesn't work.

[N Dentressangle]

andybebop said:

I believe they turn on safeguard by default.This explains how to turn it off.

https://www.postoffice.co.uk/broadband-phone/safeg...

We have a winner!!!!

Have a virtual from the newly accessible Gloucester Brewery website on me, and thanks for all the suggestions.

[andybebop]

Glad I could be of help

[Funk]

I'd still recommend changing the DNS to something independent - I use Cloudflare which is 1.1.1.1 & 1.0.0.1.

https://1.1.1.1/dns/

[ging84]

It would be weird if they setup a porn filter that breaks all https sites, but it might be that what ever they do doesn't work with TLS 1.2 which a lot of sites don't enforce yet but this one does.