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VPN/IPsec add Miscellaneous section to explain tunables, starting with PMTU/DF bit

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Ad Schellevis 2023-07-26 16:00:29 +02:00
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source/manual/vpnet.rst
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@ -296,6 +296,19 @@ In which case the following tunables need to be changed:
* :code:`net.inet.rss.bits` = **X** <-- see :doc:`rss </troubleshooting/performance>` document.
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Miscellaneous variables
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Path MTU Discovery
--------------------------
When trying to enforce path mtu discovery (`PMTU <https://en.wikipedia.org/wiki/Path_MTU_Discovery>`__), you need to make
sure packets leave the network with the :code:`DF` set. The kernel offers a tunable :code:`net.inet.ipsec.dfbit` which
offers 3 options, :code:`0`, clear the bit on packets leaving the firewall (default), :code:`1`, set the DF bit or :code:`2`
to copy the bit from the inner header.
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Diagnostics
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