Dear @Alex789 ,

Alex789 wrote

I have a process on the LAN which does device discovery on a schedule.  It isn't doing an intrusive port scan but it uses pings to identify the devices.

Whenever this is run, it triggers an event that reads "ER605 Gateway detected Large Ping attack and dropped 134 packets.".  I haven't yet found a way to whitelist this traffic.

However, it seems strange that the gateway would detect that from the LAN and drop packets by default.

Is there any way to stop this from happening or whitelist the LAN to allow ping scans? 

The detection mechanism of this router is such that the relevant alert is given only when packets exceeding 1024 bytes are detected.
We suggest that you try changing the settings on this Device Discovery program to see if you can change the Ping bytes to be smaller.

Best Regards!