It seems that some ISPs allow MTU 1500 over PPPoE (eg. BT with their FTTC links).
I tried to set it in the web interface (Shibby v100) but it takes it down back to 1492.
Does the PPPoE that comes with Tomato allow MTU 1500? Can it be allowed in the configuration?
Reference: http lists.roaringpenguin.com /pipermail/rp-pppoe/2011q2/000261.html