  <varlistentry>
  <term><emphasis remap='B'>nat-ikev1-method</emphasis></term>
  <listitem>
<para>NAT Traversal in IKEv1 is negotiated via Vendor ID options as specified in RFC 3947.
However, many implementations only support the draft version of the RFC. Libreswan sends
both the RFC and the most common draft versions (02, 02_n and 03) to maximize interoperability.
Unfortunately, there are known broken implementations of RFC 3947, notably Cisco routers that
have not been updated to the latest firmware. As the NAT-T payload is sent in the very first
packet of the initiator, there is no method to auto-detect this problem and initiate a workaround.
</para>

<para>This option allows fine tuning which of the NAT-T payloads to consider for sending and processing.
Currently the accepted values are <emphasis remap='B'>drafts</emphasis>,
<emphasis remap='B'>rfc</emphasis>, <emphasis remap='B'>both</emphasis> (the default) and
<emphasis remap='B'>none</emphasis>. To interoperate with known broken devices, use nat-ikev1-method=drafts.
To prevent the other end from triggering IKEv1 NAT-T encapsulation, set this to none. This will omit the
NAT-T payloads used to determine NAT, forcing the other end not to use encapsulation.
</para>
  </listitem>
  </varlistentry>

