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.
Internet Gateway (192.168.0.1/24) which is also DHCP Server. It's a Arris Modem. TPLink 24Port Managed Switch 19" (192.168.0.10) (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, 192.168.0.64 (connected via wired LAN) One client is a Raspberry Pi (192.168.0.76) 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 192.168.0.255
the result just shows responses from 192.168.0.1 and 192.168.0.60 (marked as DUP!).
What could be reasons that the 192.168.0.64 does not respond to the broadcast ping?
I did already successfully test "ping 192.168.0.64" 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.