Bah... Who needs "grep" if the source code is as well structured as ours? :-) Here it is: "unix/ifnet.c". We subtract UDP_IPV4_HDRSIZE and UDP_IPV6_HDRSIZE from the MTU. Shouldn't that be enough to prevent fragmentation? That's exactly the subtraction that wasn't present in "win32/ifnet.c" in 0.4.9. -Thomas