Hint: IPSEC for IPv6

  • Hey guys,
    For a long time I have had problems getting IPSEC to work with IPv6. Tunnels would be established, I could ICMP ping but never establish a TCP connection for database, HTTP etc. Finally emailed PFsense support and got this answer:


    It could be the MTU of the tunnel causing a problem. Can you try setting up MSS clamping for VPNs under System > Advanced on the Miscellaneous tab? If you check the box, try entering a value such as 1400 or 1350 to see if things behave better. Alternately, leave that setting alone and try to toggle the option to disable scrub under System > Advanced on the Firewall/NAT tab.

    IPsec in general already does not like packet fragmentation, but compounding that are some issues with pf and ipv6 fragments such as: https://redmine.pfsense.org/issues/2762, and some other known issues. Doing all you can to reduce the packet sizes should help the traffic flow properly.


    I set the MSS clamping to 1300 and its now working finally. Thought someone else could find it useful!

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