Multicast frames stop being received by Android clients on WLAN with WAP121

[pellsky]

I have a number of devices connected wirelessly to a Cisco WAP121. One device is an android phone running the zeroconf browser app to discover and display mDNS services. This all works fine for a while and then at some point, the Android phone stops receiving the responses.

From a wireshark trace running on a PC connected to the same WLAN I can see the mDNS query for services being transmitted from the Android phone. And I can see a number of responses from devices on the same WLAN. According to wireshark the layer 2 destination address of the responses is IPV4mcast_fb. The Android app stops receiving the responses. Restarting the app and/or the phone makes no difference.

Should all clients connected to the WLAN see these responses or is it possible for the AP to filter out some clients when sending out a multicast frame?

[Flavio Miranda]

Hi,

   This is the kind of problem that requires further investigation and specialized tools. If you could see the back and forth of packet between Android and AP at air interface, probably you´ll see what´s going wrong.

 However, is not easy to have a tool for that purpose easily.  

One simple verification you could try is take a look at  Status and Statistics > Radio Statistics Multicast Frames Received

—Count of MSDU frames received with the multicast bit set in the destination MAC address Multicast Frames Transmitted

—Count of successfully transmitted MSDU frames where the multicast bit was set in the destination MAC address

Try to test only with the target device and see if those counters increase. 

-If I helped you somehow, please, rate it as useful.-

[pellsky]

Thanks for your help Flavio.

I observed this on our office network but unfortunately do not have admin access to any of the networking equipment. Nobody knows the password for the AP so I can't see any statistics or configuration information. We've now replaced the AP with one from a different manufacturer and no longer see the problem. I will factory reset the WAP121 and try to reproduce the issue in a more controlled environment. But, as you say, I believe it requires a more specialized tool to see what is actually being transmitted and we do not have that available.