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<h1>F5 SSL VPN</h1>

<p>Experimental support for <a
href="https://www.f5.com/services/resources/glossary/ssl-vpn">F5 SSL
VPN</a> was added to OpenConnect in March 2021. It is also known as BIG-IP in
some documentation. It is a
<a href="https://en.wikipedia.org/wiki/Point-to-Point_Protocol">PPP</a>-based
protocol using the native PPP support which was merged into the 9.00
release.</p>

<p>F5 mode is requested by adding <tt>--protocol=f5</tt>
to the command line:
<pre>
  openconnect --protocol=f5 big-ip.example.com
</pre></p>

<p>Since <a href="http://sites.inka.de/~W1011/devel/tcp-tcp.html">TCP over
TCP is very suboptimal</a>, OpenConnect tries to always use PPP-over-DTLS,
and will only fall over to the PPP-over-TLS tunnel if that fails, or if
disabled via the <tt>--no-dtls</tt> argument.</p>

<h2>Quirks and Issues</h2>

<p>Currently, OpenConnect only supports basic username/password
authentication for F5, along with an optional TLS client certificate
and the "domain" dropdown used by some F5 VPNs. The domain form field
can be automatically populated with the <tt>--authgroup</tt> command-line option.
If you have access to an F5 VPN which uses other types of authentication (e.g.
RSA or OATH tokens), please send information to <a href="mail.html">the mailing
list</a> so that we add support to OpenConnect.</p>

<p>Connectivity over DTLS is supported. On BIG-IP server v16, it is possible to use
either DTLSv1.0 or DTLSv1.2, if configured correctly. On BIG-IP server v15, it is limited to
DTLSv1.0 because experiments show that BIG-IP server v15 cannot negotiate correctly down to
DTLSv1.0 when a newer version of DTLS is attempted.</p>

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