I'm running Jenkins in corporate environment and that means Jenkins doesn't have unlimited access to internet. All traffic goes through proxy and every allowed domain needs to be white-listed separately.

When downloading plugin updates, the downloads fail with 403 Forbidden if a new mirror has been added and https://updates.jenkins.io/download/plugins/xxx call is redirected to the not-white-listed domain.

People have to do things like this to circumvent the problem:
https://www.north-47.com/knowledge-base/update-jenkins-plugins-behind-a-corporate-proxy/

It seems unnecessary to fiddle around with the update-center.json or default.json when a simple retry to another domain could possibly be done in Jenkins? I'd think that this would be a good feature too if getting a 404 from the plugin mirror site (though that hasn't happened to me ever).

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java.io.IOException: Failed to download from https://updates.jenkins.io/download/plugins/pipeline-rest-api/2.17/pipeline-rest-api.hpi (redirected to: https://ftp.halifax.rwth-aachen.de/jenkins/plugins/pipeline-rest-api/2.17/pipeline-rest-api.hpi)
at hudson.model.UpdateCenter$UpdateCenterConfiguration.download(UpdateCenter.java:1321)
at hudson.model.UpdateCenter$DownloadJob._run(UpdateCenter.java:1869)
at hudson.model.UpdateCenter$InstallationJob._run(UpdateCenter.java:2147)
at hudson.model.UpdateCenter$DownloadJob.run(UpdateCenter.java:1843)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
at java.util.concurrent.FutureTask.run(FutureTask.java:266)
at hudson.remoting.AtmostOneThreadExecutor$Worker.run(AtmostOneThreadExecutor.java:118)
at java.lang.Thread.run(Thread.java:748)
Caused by: java.io.IOException: Failed to load https://updates.jenkins.io/download/plugins/pipeline-rest-api/2.17/pipeline-rest-api.hpi to xxx/pipeline-rest-api.jpi.tmp
at hudson.model.UpdateCenter$UpdateCenterConfiguration.download(UpdateCenter.java:1287)
... 7 more
Caused by: java.io.IOException: Unable to tunnel through proxy. Proxy returns "HTTP/1.1 403 Forbidden"
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
at sun.net.www.protocol.http.HttpURLConnection$10.run(HttpURLConnection.java:1950)
at sun.net.www.protocol.http.HttpURLConnection$10.run(HttpURLConnection.java:1945)
at java.security.AccessController.doPrivileged(Native Method)
at sun.net.www.protocol.http.HttpURLConnection.getChainedException(HttpURLConnection.java:1944)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1514)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1498)
at sun.net.www.protocol.https.HttpsURLConnectionImpl.getInputStream(HttpsURLConnectionImpl.java:268)
at hudson.model.UpdateCenter$UpdateCenterConfiguration.download(UpdateCenter.java:1280)