Please also make sure your servers are not behind a firewall. If they are you would need to configure the Proxy configuration -
Open Apache Felix Web Console and configuration tab: http://localhost:4502/system/console/configMgr
and find a "Day Commons HTTP Client". Configure proxy server here.
For more details please check following link:
http://dev.day.com/docs/en/cq/current/deploying/configuring_osgi.html