Cloudflare SaaS Custom Hostname dont fallback to the Origin

[binglu895]

What is the name of the domain?

wmoomw.dpdns.org

What is the error number?

HTTP ERROR 404

What is the error message?

HTTP ERROR 404

What is the issue you’re encountering

Cloudflare SaaS Custom Hostname dont fallback to the Origin

What feature, service or problem is this related to?

Secondary DNS

What are the steps to reproduce the issue?

1. create custome hostname and fallback origin in Cloudflare>SSL/TLS Custome Hostname：b.dpdns.org , shows Active in cloudflare Fallback Origin：origin.a.dpdns.org , shows Active in cloudflare

2. Create the ff DNS records:
   https://global.discourse-cdn.com/cloudflare/original/3X/7/8/78042ebf02c67a5d9e3fa68ebb65d5ae2fb53423.png

1.I was expecting above configurations to work: requests to b.dpdns.org should be routed to origin.a.dpdns.org by Cloudflare based on the request headers. But instead, I'm getting a 404 error. Direct access to origin.a.dpdns.org works fine. What's wrong here? 2.How to understand if a request is handled by Cloudflare SaaS? 3.How to understand if a request to the custom hostname is handled by fallback origin?

Screenshot of the error