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I'm using openVPN to connect to one EC2 instance from another. The client cannot see the server, however, despite that servers outside of AWS can see the server and successfully negotiate with it.

It fails with "Cannot resolve host address": log output here. Config here.

I speculate that this is because UDP isn't configured properly. I've already opened the UDP ports on that instance via the AWS SecurityGroups - this didn't work, both for all incoming UDP, and/or for UDP from the server IP.

Does anyone know what might be misconfigured in AWS to prevent this?

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Sounds more like a DNS problem to me. –  jamieb Jan 14 '13 at 0:42
    
I agree with @jamieb. "Cannout resolve host address" is the DNS resolver complaining that it isn't able to translate the hostname into an IP address. Can you post the config.ovpn (scrubbed of any private info such as a password or pre-shared key) –  Jeff Hall Jan 14 '13 at 2:48
    
I think your two ec2 servers might be on the same network. There might be some issue there. DNS records would normally return a 10. address. Why not just open all ports to the ec2 instance to other instances in the same security group? –  Edwin Jan 14 '13 at 6:43
    
@jamieb I'm using the exact IP address, and you can see that in the pastie. I've added my config file in the question. I can't open all ports on the VPN server (to test) because I don't control it - our sysadmins do. I'm setting up a VPN through a personal dev. env. in the cloud –  New Alexandria Jan 14 '13 at 16:56
    
It's not because of some dopey DOS line terminator problem in the ovpn config, right? The IP with a ctrl-M at the end of it may not look like an IP address on the Linux openvpn client, and it may try to resolve it. –  cjc Jan 14 '13 at 17:08
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