I'm having issues with outbound SSH connections on Ubuntu 14.04. Essentially I'm tunneling out of Azure to another cloud server (hosted on Digital Ocean). Initially I've connected ok and the tunnel has worked as expected but after a few times closing and reopening the tunnel attempts to tunnel out just hang.
Here is the SSH session:
azureuser@az-server:~$ ssh -vv -i ~/.ssh/key.pem user@do-server.com
OpenSSH_6.6.1, OpenSSL 1.0.1f 6 Jan 2014
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug2: ssh_connect: needpriv 0
debug1: Connecting to do-server.com [redacted_ip_address] port 22.
..eventually timesout
Nothing appears in the do-server's auth.log but the server is responsive to SSH connections from other computers and I'm able to reach other services on the do-server from the Azure VM:
azureuser@az-server:~$ nc -vz do-server.com 80 Connection to do-server.com 80 port [tcp/*] succeeded!
If I do not attempt to connect for a few minutes connections will start working again. Restarting the Azure VM has no effect though. It is as if the virtual network layer is refusing to route my SSH connections. I've looked through the Azure VM management UI for something related to outgoing connections but I don't see anything. I don't have any virtual or local networks configured in Azure, I'm just using the VM as a stand-alone machine.
Does anyone know if there could be some sort of filtering that I could be triggering? I'm just doing standard sort of debugging, restarting the SSH session 10 or 15 times an hour. I'd be surprised if this was being picked up as an attack of some sort.