[LARTC] To broadcast or not to broadcast...

[Grant Taylor]

I'm looking to refine / re-use my recently discussed "Redundant internet 
connections" 
(http://mailman.ds9a.nl/pipermail/lartc/2007q2/thread.html#21015) in 
such a way that I will not be sure of returning traffic, thus I must 
monitor the connection my self and not rely on inbound traffic to update 
the kernel counters.

I'm considering using arping to ping the upstream gateway.  I think this 
will work just fine.  However arping has an option to always send 
broadcasts verses starting with broadcast packets and then falling back 
to unicast packets.  My fear is that if I use arpings default method of 
broadcast and then unicast once a MAC is known, this will fail if the 
upstream router is doing something where the MAC address would change.

So, my question / request for thoughts and / or opinions, is should I 
always send out broadcasts so that any and all stations on the subnet 
see the ARP, thus allowing the arping to function even if the MAC 
address of the default gateway is changed, say if the provider decides 
to do an upgrade and / or maintenance?



Grant. . . .