Load Balancing Cannot Ping WAN Ip Add?

hi..

i’m using this method for load balancing in my network → http://wiki.mikrotik.com/wiki/Load_Balancing

everything just works perfectly except one thing, i cannot ping my wan ip address from MT Terminal Box, when i tried to ping my first / second wan ip address, i only get 2 or 3 reply in the begining, else is RTO.

i know it’s not a big problem because everything already works fine, i’m just curious..

do i need to put another mangle rules to make the ping works? because when i disable all mangle rules for load balancing, the ping to wan is working.

thanks

note:
i already had this problem since using v2.9.40 till now v3.3

anyone?