Multicast issue

[Novodk]

Hey everyone,

Just looking for a general sanity check here. I'm trying to figure out if multicast is being allowed or blocked on a client's network.

My test setup:

• Logic Machine (LM): 192.168.5.10 (KNX physical address 1.1.1)
  
• KNX IP Router: 192.168.5.11 (KNX physical address 1.2.0)
  
• Multicast Address: 224.0.23.12
  
• Filter Tables: Everything is explicitly set to "Route" on all devices.
  

What works:

• I can successfully ping the IP Router (192.168.5.11) from the Logic Machine.
  
• When connected to the LM (192.168.5.10) via ETS, I can see and control everything on line 1.1.X, and the LM UI updates perfectly.
  

The issue:

• If I connect to the IP Router (192.168.5.11) via ETS, I can only see and control things on line 1.2.X. Crucially, these telegrams are not updating or crossing over to the LM on 1.1.X
  

Based on these findings, it seems to me that standard unicast traffic (like pings) is fine, but multicast traffic is being blocked by the network switches. Is that a correct assumption?

And if so, what is the best way for me to test and prove this from my side? I want to gather as much concrete evidence as possible before I approach their IT department so they actually understand the issue and don't just brush it off.
Appreciate any advice or troubleshooting tips!