large icmp packet issue

I am having problem getting ping to work to a specific destination host when using large size icmp packet and i am hoping someone here can offer some suggestion. With regular ping, i can ping this remote host without any problem, but if i crank up the packet size to above 1500 (1500 still works), i won't get any icmp reply. My first thought was this was a pmtu issue. but when I ran tcpdump on this remote host, i saw the incoming ping requests and this host actually sent back icmp replies, so it appears that there is some device in between blocking these large size icmp reply packets. Here is the question, how can i find out which hop on the path is causing this behavior? FD