I occasionally get the following 421 error:
The client needs a new connection for this request as the requested host name does not match the Server Name Indication (SNI) in use for this connection.
However, refreshing the browser clears the error and the page loads normally. The next time loading the page will not produce and error and as such the pattern seems pretty random. The only pattern I can see is that this may happen When I am redirecting a page using header("Location: " . $url);
I have a PositiveSSL Multi-Domain Certificate from Comodo. My servers are Apache on a shared web hosting service so I don't have access to the configuration.
I load pages from one domain and within the page are links to a second domain on the certificate.
Everything I've read regarding this error seems to point to this problem being related to this being a multi-domain certificate.
What I would like to know is if there is anything on the web page (php) coding side of things that can cause this (and can be fixed) or if it is a configuration error or possibly a server error and only my hosting service can fix it.
My hosting service has so far been unable to provide anything and requested calling back with the exact time it happens next so they can research it. Any help would be appreciated as I am not overly confident they can figure this out.
I did more research and came across another article that talks about it here. Exactly what @Kevin describes. The article confirmed that it happens in Safari. So taking the advice, I set about getting separate certificates for each domain. I am on a shared host (Webhostinghub) and discovered they now offer free SSL (AutoSSL) that auto renews. It sounded to good to be true. They set me up with 5 free certificates. So far so good. I may even try to re-enable the static domains to test. If this all works, I'll save $ to boot as a bonus and let my Comodo certificates expire in July.