The question came up when trying to integrate my KNX-IP interface via the java Calimero library. My implementation (running on the Raspberry - via WLAN) did not find the KNX IP interface, so I started deeper investigation. Meanwhile I disabled "Multicast" on software side in the KNX integration (and now software finds the KNX IP interface), but I still want to understand why a broadcast ping (ICMP) is answered just by some clients.

Network Infrastructure:

Internet Gateway ( which is also DHCP Server. It's a Arris Modem.
TPLink 24Port Managed Switch 19" ( (T1600G-28TS). One port is directly connected to the Internet Gateway / DHCP.
3 Unifi Ubiquity WLAN APs, each of them connected to the TPLink Switch
Several clients, one of them is a Windows PC, (connected via wired LAN)
One client is a Raspberry Pi ( with Raspbian Stretch, connected via WLAN and one of the ubiquity APs.
another client is the KNX IP interface (connected via wired LAN)

When I execute on the raspberry the

ping -b

the result just shows responses from and (marked as DUP!).

What could be reasons that the does not respond to the broadcast ping?

I did already successfully test "ping" on the windows pc to verify it responds to PING. So I assume it must be one of

the settings in the TPLink Switch?
the settings in the Ubiquity WLAN AP?

But I don't find which settig could be the reason - as it isn't LAN to WLAN broadcast but WLAN to LAN broadcast...

In the TPLink switch, the "Unknown Multicast" option is already enabled.

closed as off-topic by Gerald Schneider, wazoox, Jim B, Ward Mar 21 at 15:42

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Ping is only going to show you a few of the responses. If you want to see all the responses that are received then run a packet capture, filter for ICMP, and then ping that broadcast address and analyze the capture results.

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