If your firewall blocks all traffic to all non-whitelisted IPs then you can start by allowing 

*.pubnub.com, *.pndsn.com, *.pubnub.net and *.pubnub.io.


If your firewall requires specific IP whitelisting then you must be on a paid plan.


Please, contact PubNub Support for the full list of publicly accessible inbound and outbound PubNub Network IP addresses.