I'm currently doing the following on no-ip to get around my ISP blocking inbound traffic to port 80.
I have one domain pointing to a local IP. Since this is a dynamic IP I've got their client to dynamically change the IP within no-ip once it changes. I'll call this "a.net".
I have another domain pointing to "a.net:8081", called "b.net". This is a URL redirect record.

I then bought a domain name off NameCheap, called "c.com", and wanted to point it at "b.net". I added a CNAME record and set the host to 'no-ip' with value 'b.net'. When I access "c.com", I just get "Server not found".

Accessing "b.net" in the browser works, as well as accessing "a.net:8081", so I figured maybe the CNAME is taking some time to propagate. But just maybe CNAMEs don't work on URL redirects. Any suggestions what I'm doing wrong?