That info about being on a network is a little out of date. LW now has the ability to connect easily with such users. No need to ban such addresses. Only problem being that nobody will be able to direct connect with such users.

But still, it does show that you're not configured properly. And it is as a result of your router. You either need to enable UPnP or manual port forward. See these sections here Connection problems? Check here first! (click on link)

The term Force IP has been replaced. It is no longer used. It has been replaced with port forwarding. eg: Manual port forward instructions & sample image. But see the above link about connections to get full instructions about the whole process.