yes, I am aware of this, but if problem is not elsewhere, then every self respecting router or firewall should handle this. In fact, I have also tried many hardware (D-Link, Juniper, Extreme Networks, etc.) and software (OpenWRT, Coyote, Zeroshell) routers, and pfSense was only what did not pass these packets. This was very surprising to me, that such trivial problem exists in any other way - excellent router software, for a long time, and nobody care about that.