Multicast traffic filtered by NWA50AX AP

jojo42

Hello,

I have a wired device on my local LAN hosting services that are discovered by mDNS. The multicast packets are filtered by the wireless AP (NWA50AX) before they arrive to the wireless clients. Is there a way to disable multicast filtering on the AP?

Thank you.

Zyxel_Nami

Hi @jojo42

The NWA50AX AP is generally not designed to filter out multicast packets. Could you please elaborate on how you observed that the AP is filtering multicast packets? This information will help us better understand your issue.

jojo42

Thank you for your answer. I have a raspberry pi hosting a Samba and Airplay server that is wired to a switch. My AP is also wired to the same switch.

Multicast traffic between wireless devices on the same AP seems to work back and forth with no problem.

Multicast traffic between the raspberry pi and other wired devices also works fine.

But, multicast traffic only seems to work one way between wired and wireless devices. The raspberry pi will receive multicast queries sent from a wireless client (wireless client →
NWA50AX → switch → raspberry) but the replies seem to be blocked at the NWA50AX (raspberry → switch → NWA50AX → ???)

This behavior doesn't always happen. Sometimes it will work just fine and other times it won't. This is why i'm wondering if the AP wouldn't trigger some filtering or rate limiting of some kind.

Thank you

Zyxel_Nami

Hello @jojo42

Could you please let us know which model of Switch you are using?

Besides, please enable Zyxel Support Access on Nebula for us to further investigate your issue, and please send me your Org/Site name via private message.

jojo42

I tried two switches: the first one is the embedded switch of the router provided by my ISP (Orange Livebox) and the other one is an unmanaged Netgear GS308 switch.

tcpdump shows the raspberry (plugged on the same switch as the API) receives multicast queries from the wireless clients of the AP, but tcpdump on a wireless client doesn't show the replies sent from the raspberry. This is why I'm suspecting that the NWA50AX filters some of the packets. I doubt that the "dumb" switches I'm using would do any kind of snooping or storm control.

Zyxel_Nami

Hello @jojo42

Sorry for the late response. I received your message.

To further diagnose where the packet might be getting lost, we suggest performing a tcpdump test on the AP.

Here are the commands to execute:

1. To capture packets on the wired interface (eth0): packet-trace interface eth0 verbose-vvv
2. To capture packets on the wireless interface (for example: wlan-2-1): packet-trace interface wlan-2-1 verbose-vvv. To know which WLAN interface, use this command: show wlan slot_name detail.

For example: I want to trace packets on the SSID 'WAC_Nami' that my devices connect to. The corresponding WLAN interface is 'wlan-2-1'

Please share the result screenshot with us via PM.

Thank you for your cooperation.

jojo42

Hello,

The packets appear on both interfaces:

eth:

19:01:54.162932 IP (tos 0x0, ttl 255, id 848, offset 0, flags [DF], proto UDP (17), length 358)
192.168.1.250.5353 > 224.0.0.251.5353: [udp sum ok] 0*- [0q] 6/0/0 _raop._tcp.local. [1h15m] PTR 74FECEABEB2D@raspberrypi._raop._tcp.local., 74FECEABEB2D@raspberrypi._raop._tcp.local. (Cache flush) [1h15m] TXT "sf=0x4" "fv=76400.10" "am=ShairportSync" "vs=105.1" "tp=TCP,UDP" "vn=65537" "md=0,2" "ss=16" "sr=44100" "da=true" "sv=false" "et=0,1" "ek=1" "cn=0,1" "ch=2" "txtvers=1" "pw=false", 74FECEABEB2D@raspberrypi._raop._tcp.local. (Cache flush) [2m] SRV raspberrypi.local.:5000 0 0, raspberrypi.local. (Cache flush) [2m] AAAA 2a01:::250, raspberrypi.local. (Cache flush) [2m] AAAA 2a01:::ae55, raspberrypi.local. (Cache flush) [2m] A 192.168.1.250 (330)

wlan:

19:01:54.163158 IP 192.168.1.250.5353 > 224.0.0.251.5353: 0*- [0q] 6/0/0 PTR 74FECEABEB2D@raspberrypi._raop._tcp.local., (Cache flush) TXT "sf=0x4" "fv=76400.10" "am=ShairportSync" "vs=105.1" "tp=TCP,UDP" "vn=65537" "md=0,2" "ss=16" "sr=44100" "da=true" "sv=false" "et=0,1" "ek=1" "cn=0,1" "ch=2" "txtvers=1" "pw=false", (Cache flush) SRV raspberrypi.local.:5000 0 0, (Cache flush) AAAA 2a01:::250, (Cache flush) AAAA 2a01:::ae55, (Cache flush) A 192.168.1.250 (330)

But on a wireless client connected to the AP I do not receive them…

Zyxel_Nami

Hi @jojo42

From the provided packet traces, it's evident that multicast packets are being broadcasted on both the ethernet and WLAN interfaces of the AP.

Given this, it would be beneficial to check the settings of your wireless clients to ensure they are configured to receive multicast packets.