Broadcasts On OS X - Oops!

[Alex Tweedly]

Brent Anderson wrote:
> Hello.
>
> I think that the point was to use broadcasts not to use another 
> address. I've found the same problem on OS X where when you write 
> packets to a .255 address they don't get routed across the network, as 
> if it were a regular address. In looking back on other threads on this 
> subject, it's been noted that this is a bug in Mac OS X, so it may not 
> be possible. Am I mistaken in this, or is that just the sad truth of 
> it all?
Hmmmm - what exactly do you mean by "they don't get routed across the 
network" ?

A subnet broadcast packet (i.e. to a .255 address, for most of us), 
*should* be sent on the local network segment (i.e. delivered to each 
device connected on the same subnet).

It should *not* be forwarded by any router attached to the network 
segment (ignore the special case where you send a subnet broadcast to a 
subnet other than the one you are connected to, and the router is 
suitably configured :-)

It is certainly possible to send a broadcast packet from OSX (e.g. you 
can do "ping 192.168.1.255" and it works correctly), but I don't know 
whether or not it is possible to do it from Rev. I'll play with it some 
more later tonight when I can have more than one machine on my network ....
>
> Although this is more of a hack than anything, you could use a loop 
> from 1 to 254 and use the current hosts IP address to emulate the 
> effect of a broadcast.
Indeed a hack - beware of flooding the network with back-to-back packets 
.....

-- 

Alex Tweedly      mailto:alex at tweedly.net      www.tweedly.net