I'm guessing you are talking about accessing your router's web interface using HTTPS. If you use the self-signed cert from the router, then you will always still see a warning. Browsers will show a warning for self-signed certs; you have to get a cert signed from a CA to get rid of the warning. The traffic between your browser and router is still encrypted.
Looking for advice on how to update / fix the SSL certificate with my AX88U running Merlin 386.8 Today I went to login to https://router.asus.com:8443/Main_Login.asp and got a Chrome warning the certificate was invalid. I set up the 88U with SSL around 10 months ago if I remember correctly and...
The certificate available from the router has a domain name - in my case the DDNS domain. I found an easy way round this by using that domain name for the router on the internal network by setting the domain name in the lan settings.
Works sweet as a nut but I'm ready for criticism from admitting this.
As an example if the domain is squiggle.ddns.net the I do this for the lan
And on the dhcp page
Works 100% and gives everything on the lan a.ddns.net name. I can access my NAS with nas.ddns.net or my settop box with sh1.ddns.net
It doesn't really improve the security any (which on the lan isn't a concern) but it does satisfy the browsers and gives me a warm glow knowing I sorted that myself.