VPLS bigger than 1558 did not works in v7.11
but if one of the PE’s using v6 it works like a charm.
i did change both PW control domain into “default” and “Enabled”, both are has the same result.
See all the details in http://forum.mikrotik.com/t/vpls-mtu-problem-on-v7-7-9beta4/165519/8
thx