Thanks serpentFly, but the problem doesn’t seem to be on Win Xp, but only occurs in Win 7 and beyond. Does it got to do anything with driver? i’m using 188.8.131.52 version ndisapi driver.
Also what i noticed in Win7 was the SendARP() call in tunnel mode having client IP as parameter would actually fail when called from StarNat(). To resolve this problem i added a filter to exclude In/Out of ARP packets and that seemed to solve the problem. But now we face the issue of packets getting dropped. Let me know is anything wrong in our apporach?
Also it would help us to point out at better ways to optimize it further.