I'm in charge of linking our Web Server at Rackspace Cloud (LAMP) to a local telecom company server via VPN. As I'm not an expert in this area, I decide to use OpenVPN on top of our server (CentOS 6) 'cause I thought that would be ready to use in less than an hour; however, as I mentioned that I'm not an expert in this field, I'm facing difficulties to understand the remote server specifications.

Here is the details provided by telecom company:

VPN Device Tunnel Endpoint IP Address: 91.151.a.b

Host(s): IP Address(es) to be accessed (Public IP address required): 91.151.c.d

Phase 1 & 2 Encryption Type: 3DES/SHA1

VPN Scheme: IKE

Phase 1 encryptin algorithm: 3DES

Phase 1 hash algorithm: Secure Hash Standard

Phase 1 authentication method: Pre-Shared Key

Phase 1 algorithm: Diffie-Hellman Group 2 (1024 bit)

Phase 1 lifetime: 86400 seconds

Phase 2 perfect forward secrecy (yes/no): No

Phase 2 encryption algorithm: 3DES

Phase 2 hash algorithm: Secure Hash Standard

Phase 2 lifetime: 3600 seconds

They asked me to send them back our details, exactly in the same format.

My questions:

  1. There are so many tutorials explaining how to configure the OpenVPN in different ways. I've read a few of them but all of them are explaining different configurations. Is there any resource I can find a how-to or hint for configuring our machine in a proper way which fits our needs? Even if you give me some keywords to search, that would be great.
  2. Do I need to set up our OpenVPN exactly in the same way they have configured their device?
  3. I need the Subnet Mask for the Tunnel Endpoint IP Address, right?
  4. They said we can exchange the key via SMS! Which key they exactly asked us to send them via text message and is that normal texting the VPN key to the partner organisation?

The VPN information provided by the telecom are for IPsec, OpenVPN uses its own, SSL-based protocol. You might configure IPSec under Debian or RedHat. A generic IPSec Howto is also available, but it seems a bit outdated. You might also want to check ipsec-tools homepage.

As for your last question - exchanging the PSK keys via SMS is a common practice, though there are safer alternatives.

  • Thanks mateusz for the answer. by the way, you mean that it's impossible to use OpenVPN in this case, right? – Mahdi Jan 31 '13 at 13:18
  • No, you can't use OpenVPN in this case. – mateusz.kijowski Jan 31 '13 at 13:22

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