https://stelfox.net/notes/protocols/Recent content in Protocols on ./Sam_Stelfox.shHugoen-USCopyright © 2008, Sam Stelfox, all rights reserved.https://stelfox.net/notes/protocols/gre-tunnel/Mon, 09 Oct 2017 22:14:23 +0000https://stelfox.net/notes/protocols/gre-tunnel/<p>GRE (Generic Routing Encapsulation) wraps layer 3 traffic inside IP protocol 47 packets, creating a simple point-to-point tunnel between two hosts. The tunnel itself is unencrypted, so pair it with IPSec or WireGuard if you need confidentiality.</p> <h2 id="quick-setup">Quick Setup</h2><p>Two hosts connecting their private networks through a GRE tunnel. Use a dedicated /30 for the inner tunnel addresses that does not overlap with anything else on either side.</p> <table> <thead> <tr> <th></th> <th>Host 1</th> <th>Host 2</th> </tr> </thead> <tbody> <tr> <td>Public IP</td> <td>1.2.3.4</td> <td>4.3.2.1</td> </tr> <tr> <td>Tunnel IP</td> <td>172.16.10.1</td> <td>172.16.10.2</td> </tr> <tr> <td>Private network</td> <td>10.0.0.0/24</td> <td>10.16.0.0/24</td> </tr> </tbody> </table> <p>On Host 1:</p>