On Wed, 30 Dec 2015 23:36:22 GMT "Steve Simon" <st...@quintile.net> wrote: > > It is not a common factor if you ping broadcast. > > Yep, fair point.
If you're pinging plan9 machines, printing source address is not useful as they sebd ping replies with source = broadcast ip address. You have to look at the source ether addr to find out which machine responded. > I admit I have never done a ping broadcast. > > I did hear a story of somone who (in the early days of ethernet) > built a ping broadcast packet, with the source address of the broadcast addre > ss. > > This resulted in the mother of all packet storms. > > Maybe apocryphal, but a nice story none the less. Seems apocryphal or must've been very early days! Ping consists of sending an ICMP request packet, followed by the responder(s) sending back ICMP reply packat(s). No ICMP errors are sent in response to any ICMP message to avoid just such a storm. Ages ago you could send a *directed* broadcast to a place far away, which would get routed to the right subnet and many or all machines on that subnet would respond. Back then the 'Net was a friendlier place and people didn't use NAT and script kiddies were rather rare. All that changed a couple decades ago.