[Zope] Limit Zope only from Pound

Hello, I have installed pound and zope in different machines. Pound is a IP: 192.168.1.1 and Zope is in IP: 192.168.1.5:8080. Pound balances to Zope, correctly. Although, I want than Zope does not visible from external, that is to say, Zope is only accessible from Pound (and not with http://192.168.1.5:8080 manually) . I have tried con "ip-address", but it does not run. Anybody do knows how do it ? Thanks !