Você precisará de um roteador que suporte a funcionalidade de loopback.
Many DSL routers/modems prevent loopback connections as a security feature. This means that a machine on your local network (e.g. behind your DSL router/modem) cannot connect to a forward facing IP address (such as 199.149.252.44) of a machine that it also on your local network. Connecting to the local IP address (such as 192.168.2.40) of that same machine works fine.
Fonte: link
Este tópico em discussão discute as implicações de segurança (ou a falta delas): link