Doc extra settings for group license if docker host is Windows or MacOS

docs/how-to/register.rst

@@ -218,6 +218,18 @@ In docker container, register Pyarmor with same device regfile. For example::
 
 When need to verify license, the docker container will send request to docker host.
 
+.. important::
+
+   When docker host is MacOS or Windows, it may need extra settings for `host.docker.internal` in docker container to make sure ip address of docker container is in the same network with `host.docker.internal`.
+
+   For example, docker container has ip address ``172.17.0.2``, if `host.docker.internal` is not starts with `172.17.x.x`, try to add one extra line in `/etc/hosts` in docker container::
+
+       host.docker.internal 172.17.0.1
+
+    In docker host, also make sure `pyarmor-auth` could listen on `172.17.0.1`, refer to `issue 1542`__
+
+__ https://github.com/dashingsoft/pyarmor/issues/1542
+
 Using group license in CI pipeline
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