How to use mirrorOf in Maven

Question

What is the difference between using

<mirrorOf>central</mirrorOf>

and

   <mirrorOf>*</mirrorOf>

We have a Nexus server running proxied to the Maven public repository and using "*" instead of "central" downloads some artifiacts but not all.

Reading http://maven.apache.org/guides/mini/guide-mirror-settings.html does not suggest what could cause this ?

Answer 1

<mirrorOf>central</mirrorOf>

says if request comes to lookup for central maven repository look in its mirror instead

where

<mirrorOf>*</mirrorOf>

says for any request to download from any repository look in this mirrored repository

if you have second and if it is failing to download some artifacts it could be because you are not proxying certain repository in your own nexus repository