Hi, Which version of NS are you using. The ping protocol is also inbuilt in NS and the code for the same exists at ns-2.2*/apps/ping.h and ns-2.2*/apps/ping.cc. So are u recompiling the ns with new ping after doing some changes?
neways try using the syntax hdr_ip* hdrip = HDR_IP(pkt); Also if it still doesnt work, post the entire error message that you obtain while recompiling the NS Regards Sanjay Raghani Mtech II CSE IIT - Roorkee