Is DynDNS with https supported?

Yes. CDRouter can test Dynamic DNS clients running over https if the CPE can either be configured with a new root CA certificate or configured to skip certificate validation. To enable the DynDNS server to run in https mode, configure the following testvar:

testvar dynDnsTransport https

By default, CDRouter will use the server certificate /usr/cdrouter/tests/members.dyndns.org.pem. This certificate is a self-signed certificate signed by the root CA /usr/cdrouter/tests/root.pem. In order to validate the server certificate, the client must install the additional root CA.

Unfortunately, CDRouter can not test https://members.dyndns.org without requiring a new certificate CA since it is impossible for CDRouter to simulate the real https://members.dyndns.org using certificates from a trusted CA.