Btw, the effect described here looks very similar, checksum errors on a SYN reply with IPv6 and pf: http://lists.freebsd.org/pipermail/freebsd-stable/2012-July/068990.html Regression with jails/IPv6/pf Matthew Seaman <m.seaman at infracaninophile.co.uk> Thu Jul 26 23:10:43 UTC 2012 Mark