When the origin server identifies the requests from AgileCDN, the requests might be blocked(HTTPCODE 502). To solve this issue, you can check the logs for reasons or avoid extra analysis by enabling [Header Passthrough] function with the following steps.
Step 1. Log in to AgileCDN dashboard.
Step 2. Click CDN Management, select the CDN domain and click Modify.
Step 3. Enable [Header Passthrough].
Difference between enabling Header Passthrough and disabling Header Passthrough，here "CDN-dynamic.coc3.com(origin sever-origin.coc3.com)" as an example.
1. If Header Passthrough function is not enabled, origin server will receive the CDN request like below.
2. When the Header Passthrough function is enabled, the request headers such as UA, Host, some CloudFront headers, headers of end-users will be sent to the origin server. Here is an example of such a request.
In the end, the root cause is that the original server only allow some specified domain to be accessed, so we can also add a Host to the original server to solve the problem, how to add a new host to nginx or apache server? please search by yourself.