I've setup a VOIP server on one of my Google Compute instances. I've opened all tcp/udp ports, yes it's a bad idea, but at this point I'm troubleshooting, so it's okay because later I will lock it down.
However there is an issue, and I'm trying to figure out is it a Google firewall issue or a VOIP server config. The issue is that the traffic from the VOIP server to the cellphone who is calling is not being streamed.
I concluded this because I can't hear sound on my cellphone when I make a test call, I can however hear myself on the soft phone.
My question is about when I add a firewall rule tcp:1-65535 and udp:1-65535 and stop the iptables on my Centos 6.7 server. Does that mean that essentially all inbound/outbound communication is enabled? Is it safe to rule out the Google firewall? If the firewall is still blocking my outgoing traffic, how do I get pass that?
Traffic coming in is not the same as traffic going out. Duh, right? But here's the thing, if you're running on a google network ( the equivalent of an AWS::VPC ) and you are not using a proxy server ( or NAT ) then your traffic will not be going out like you think.
Since you're trouble shooting, you might want to give your instance an external IP and see if anything changes. If you already have one, then you might have a different problem. In either case you can also use tcpdump to sniff the outbound traffic to see if it's even trying to leave the instance:
tcpdump -i eth0 port VOIP_PORT