In the Microchip TCP/IP stack arp.c, KS_ARP_IP_MULTICAST_HACK is defined. What does this do? What happens if I undefine it? I'm currently having a problem with a product "messing up" a product that is doing a multicast to 239.3.2.1 port 1234 . Is it possible that the Microchip stack is responding to this causing the issue? This is at a remote site, so I can't WireShark it. What are the expected effects of commenting out this define? THANKS! Harold --=20 FCC Rules Updated Daily at http://www.hallikainen.com - Advertising opportunities available! Not sent from an iPhone. --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .