Broadcast packet not forwarded by AP unless a client is connected to it

Broadcast packet not forwarded by AP unless a client is connected to it

Broadcast packet not forwarded by AP unless a client is connected to it
Broadcast packet not forwarded by AP unless a client is connected to it
2024-07-01 14:01:29
Model: ER706W   EAP650-Wall  
Hardware Version: V1
Firmware Version: 1.1.6

Hello !

Configuration used : 
ER706W router v1.0 v1.0.4 
EAP650-Wall(EU) v1.0 v1.1.6
TL-SG1005P PoE Switch to supply the EAP.

Omada controller opened on a laptop wired to the ER706W with a RJ45 cable.

Router and EAP have the same OPEN Wi-Fi network, Router is on channel 1 and EAP is on channel 6.

 

Here's my problem: I have a client connected to the router via Wi-Fi, which sends UDP broadcast packets on address 255:255:255:255. If I don't have another client connected to this specific AP, the broadcast packets can't be seen by any other device in promiscuous/Wireshark mode (i.e. the router doesn't retransmit them because it doesn't have any other clients).

 

I understand that this is a kind of power-saving feature for an AP, not to send packets if it has no clients. But for my application, it's not wanted.

If the broadcasting client is connected to the AP of the router, on channel 1, and no client is connected to the EAP on channel 6, then the broadcast packet will not be retransmitted by the EAP on channel 6.

 

Is it possible to force retransmission even though no other clients are connected? I've tried disabling UAPSD on both devices, but nothing works.
Only connecting another client on a specific AP enables the AP to retransmit these broadcasts.

 

Thanks, have a great day,
Evan J.

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6 Reply
Re:Broadcast packet not forwarded by AP unless a client is connected to it
2024-07-02 07:12:45

 Hi, @evoon 

Where is the Wireshark client plugged in when no client connecting to the EAP? Is it a wired client plugged into the router or a wireless client?

Currently, wifi sniffer is only able to sniff packets on a specific channel. That is to say, if the wireshark client is connecting to router's wifi (channel1), it won't sniff packets sent to EAP's wifi(channel6). For more details, you can check How to Capture the Wireless Packets on MacBook

You can mirror the downlink port of the router and capture the packets to see if the broadcast packets are sent to the EAP or not.

Or you can plug a wired client on the ETH port of the EAP and capture packets.

 

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Re:Broadcast packet not forwarded by AP unless a client is connected to it
2024-07-02 07:32:27 - last edited 2024-07-02 07:36:32

Sorry, I forgot to mention that the Wireshark PC is in monitor mode. So, it listens to packets in the air (not connected either by RJ45 cable or Wi-Fi connection). At no time is it a client. When I can't see the broadcast packet in the air, is when there is really only one wireless client, which is the broadcasting client. Although there is always one wired client—my laptop connected via RJ45 to the router with the Omada controller up. The Wireshark PC is not the same as the laptop with Omada .

 

On the monitoring device, I can only see the packet in the air retransmitted by one specific AP when another client, different from the broadcasting one, is connected to this specific AP by a wireless connection. I can dynamically switch channels while scanning in Wireshark, so it is not a channel misunderstanding. The PC connected to the router with Omada can see the broadcast packets coming through its Ethernet port.

 

The conclusion of my testing is that if there are no other wireless clients, the packet is not retransmitted in the air. If there is another client, connected with a wire, the packet is retransmitted through the wire, and not in the air. Thanks for your help.

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#3
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Re:Broadcast packet not forwarded by AP unless a client is connected to it
2024-07-02 09:37:08

 Hi @evoon 

By not retransmitting the broadcast packets when there is no client connected, the AP is effectively reducing unnecessary network traffic. This can help in optimizing the network performance by avoiding unnecessary data transmissions.

 

May we know your network scenario and why you want this?

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#4
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Re:Broadcast packet not forwarded by AP unless a client is connected to it
2024-07-02 11:49:55 - last edited 2024-07-02 11:57:26

  @Vincent-TP 

Network scenario:
1 UDP broadcast emitter, connected to the open Wi-Fi and not moving.
Multiple APs as well, all on the same open Wi-Fi network.

The emitter sends UDP broadcasts multiple times per second. These broadcast packets need to be retransmitted by all APs to ensure full broadcast coverage of a zone.

Multiple receivers are spread around the APs but are not connected in any way to the Wi-Fi. The objective for the receivers is to listen to the broadcast packets from the emitter without being connected, by "sniffing"/"monitoring" the traffic on certain channels.

I currently have it 100% working with a useless device connected to each AP to force each AP to retransmit the broadcast packets.


Why don't I simply connect the receivers to the Wi-Fi network? Because the receivers will be moving between the APs, and the 802.11r roaming tests I have conducted were not 100% consistent. Not having to reconnect when moving between APs is gold.

So my question is: Is it possible to disable this energy-saving/optimizing feature?

 

I don't know if this is relevant, but I think WoW or WoL magic packets are sent to offline devices. So, in some cases, packets are retransmitted without a connected client. I am also wondering if I could disguise my packets like that to have them retransmitted.

Thanks for your time.

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#5
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Re:Broadcast packet not forwarded by AP unless a client is connected to it
2024-07-03 01:45:58

 Hi, @evoon 

 

Thank you so much for taking the time to post the issue on TP-Link community! To better assist you, I've created a support ticket via your registered email address and escalated it to our support engineer to look into the issue. The ticket ID is TKID240705452, please check your email box and ensure the support email is well received. Thanks! Once the issue is addressed or resolved, welcome to update this topic thread with your solution to help others who may encounter the same issue as you did. Many thanks for your great cooperation and patience!

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#6
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Re:Broadcast packet not forwarded by AP unless a client is connected to it
2024-07-09 07:33:00

  @Vincent-TP 

Hello,

The final answer to this subject is that they are not planning to make this feature disableable.

Have a great day,
evoon

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