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47 lines
2.4 KiB
ReStructuredText
47 lines
2.4 KiB
ReStructuredText
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===========================
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Normalization
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===========================
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Traffic normalization protects internal machines against inconsistencies in Internet protocols and implementations.
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OPNsense has some generic options to normalize some packets on a per interface basis, in some cases
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more detailed changes are needed, for which custom rules can be configured.
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By default (when **Disable interface scrub** is not set), all interfaces are scrubbed for all traffic,
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with :code:`fragment reassemble` enabled and :code:`max-mss` set when specified in **MSS** on the interface.
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.. Note::
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Some protocols, such as NFS, require specific fragment handling options, which my require specific options set like
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**IP Do-Not-Fragment***
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--------------------
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Settings
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--------------------
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Normalization rules use the same kind of matching as normal firewall rules, which we are not going to detail here.
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When matched, some different options can be set.
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.. Note::
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When rules overlap, the first matching rule wins, hence per interface options are sorted after user configurable
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ones.
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=====================================================================================================================
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==================================== ===============================================================================
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Max mss Enforces a maximum MSS for matching TCP packets. Can also be configured on
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the interface as general rule.
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TOS / DSCP Enforces a TOS/DCP for matching IP packets.
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Minimum TTL Enforces a minimum TTL for matching IP packets.
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Do not fragment Clears the :code:`dont-fragment` bit for a matching IP packet, which
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disables
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`IP fragmentation <https://en.wikipedia.org/wiki/IP_fragmentation>`__ when set.
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Random ID Replaces the IP identification field with random values to compensate for
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predictable values generated by many hosts.
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This option only applies to packets that are not fragmented
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after the optional fragment reassembly.
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==================================== ===============================================================================
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