ICMP alerts from broadcast?

["Johnson, David" <DJohnson () IronMountain com>]

Hello all,

I'm new to IDS and have set up a Snort machine in my DMZ.  Within the first
day, activity looks pretty light, but I'm getting hundreds of "ICMP
Destination Unreachable (Port Unreachable)" alerts logged with a source
address that matches the broadcast address for my DMZ's subnet.  Most of
these alerts show a destination address of the snort machine itself, but
some also show destinations of 4 other DMZ machines.

Do I have something to worry about here (as in spoofed packets) or is this
harmless chatter?

Thanks for the help.