Jool is an Open Source SIIT and NAT64 for Linux.


Warning The project’s development has slowed down to essential maintenance. Bugfixing and support will remain active, but there will be no new features in the foreseeable future.

  • The most mature version is 4.1.8.
  • The second release candidate for version 4.2.0 is also available now.
  • jool.mx is no longer maintained. Please use https://nicmx.github.io/Jool instead.


Latest News


Version 4.1.8 has been released.

  • #366, #375: Fix checksums in Slow Path.
    This is a fairly critical bug; please upgrade. It affects packets that fulfill the following conditions:
    • IPv4-to-IPv6
    • Not ICMP error
    • Incoming packet’s DF was disabled
    • Packet was large, or GRO-aggregated
  • Add validation to more verbosely reject IPv6 packets that contain more than one fragment header.
  • Add validation to more verbosely reject fragmented (and not reassembled by nf_defrag_ipv*) ICMP errors.
    (Aside from being fairly illegal, these packets cannot be translated because the “ICMPv6 length” of the ICMP pseudoheader is unknown.)
  • Bugfix: When routing TCP/UDP fragments, the code was including header ports even though nonzero fragment-offset packets lack TCP/UDP headers.
    This bug probably doesn’t affect you, unless your routing is somehow port-based.

Also, please consider answering the survey above.


jool.mx has been abandoned. It still exists, but I cannot update it anymore. Please use https://nicmx.github.io/Jool instead.

Jool 4.1.8 was released over a month ago. Please upgrade; 4.1.7 has an important bug.

Also, please consider answering the survey.