7

I understand PPTP is widely used still, but insecure. A convenient alternative is: L2TP+IPSEC.

How secure is it?

What steps in the server setup can I take to maintain a high degree of compatibility with Windows 7+ and OSX clients and still maintain strong security? For example, defining what encryption algorithms are available such as blowfish, aes-256 and 3des, DH-Group options etc.

5

PPTP is incredibly insecure as you've stated and provides next to no security whatsoever, there are tons of vulnerabilities in it and should be avoided at all costs. You can read more about those vulnerabilities here if you scroll down to Security


L2TP should always obviously be used with IPSec because L2TP doesn't actually feature any encryption if you run it as a standalone, which is why you will mostly see it paired with IPSec


IPSec tends to be pretty secure. Below is a list of the Cryptographic algorithms used in IPSec

  • Authenticity & Integrity Protection HMAC-SHA1/SHA2
  • Confidentiality 3DES-CBC it can also use AES-CBC and AES-GCM it's worth noting that AES-GCM will also do authentication, so that could be a reason for choosing it.

Forgot to add that IPSec will also perform a Diffie Hellman exchange before data is ever sent across a link.

You can refer to RFC7321 to learn more about IPSec here is a very, exceptional article on Cisco forums on how IPSec actually works, I'd highly recommend reading it as it goes into a lot more detail than my post.

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