Docker IIS Network Connection to External Network
You can easily check connectivity to external world from your container. Just login to it and try to issue the same call from there. It can be multitude of issues and simplest one can be firewall running on your container host. For me for example unless I stop Mcafee firewall it's not going to work since Mcafee firewall sees traffic coming from 172.x subnet (which container will be run on by default) and it blocks it.