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RUT500 does not forward UDP frame from ethernet to wifi

0 votes
360 views 8 comments
by anonymous
Hi,

i have a system with two devices connected to a RUT500 using ethernet, and I want to expand it to allow the connection of wireless devices (smartphone).

For so the system sends a periodic UDP frame to the broadcast address 192.168.17.255. The smarphone is supposed to receive it, then answer. Then the system will know the ip address of the smartphone and start a two-way point-to-point conversation.

The problem is that the system does send the UDP frame over ethernet (checked using a hub and Wireshark), but any device connected to the wifi of the RUT500 does NOT receive those frames.

The other wireless services of the RUT500 seem correct; in particular, it is possible to connect to the WEBUI from a computer using wifi.

Is there something in the configuration that could prevent the UDP frames to be forwarded? The problem only applies to my system, as the RUT500 also connects together a group of Sonoff devices using the KNX protocol, which is based on UDP and works perfectly.

1 Answer

0 votes
by
Hi,

There is no default configuration that prevents UDP traffic to be forwarded.

Is your system on same LAN network?

Anthony
by anonymous
Yes, all the system is on the subnet 192.168.17.x on ethernet, and when I connect my smartphone to the system wifi, it is given an address within the same subnet.
by

Hi,

Then there is not rule that could prevent UDP traffic. Check your system settings and use tcpdump to scan traffic.

Tcpdump can be downloaded from the Package Manager. Access CLI and type: tcpdump -n -i wlan0 broadcast

Broadcast traffic will be scan so to troubleshoot your issue.

Regards

by anonymous
I am not sure this is available on windows 10?
by

Hi,

It can be downloaded via the WebUI (Services > Package Manager) on the RUT device running RUTOS (FW version 7) or via the CLI for Legacy FW with: opkg install tcpdump

Regards

by anonymous
My router is a RUT500 with firmware 2.29. It does not have the CLI option in the services menu.
by

Hi,

You can use Putty software to access the CLI via SSH. Here is a wiki article for it: https://wiki.teltonika-networks.com/view/Command_Line_Interfaces#Windows

Regards

by anonymous
Thank you, I could use tcpdump on my router following your informations.

If I dump the ethernet interface, I see the broadcast UDP frames sent by device 192.168.17.80, as in the following excerpt:

04:56:54.559079 IP Teltonika.lan.www > 192.168.17.80.37284: Flags [.], ack 75, win 14600, length 0

04:56:54.577480 IP 192.168.17.80.8001 > 192.168.17.255.9002: UDP, length 40

04:56:55.078359 ARP, Request who-has Teltonika.lan tell 192.168.17.80, length 46

04:56:55.078748 ARP, Reply Teltonika.lan is-at 00:1e:42:12:61:cc (oui Unknown), length 28

04:56:55.079129 IP 192.168.17.80.37285 > Teltonika.lan.www: Flags [S], seq 1818744915, win 2048, options [mss 1460], length 0

04:56:55.079912 IP Teltonika.lan.www > 192.168.17.80.37285: Flags [S.], seq 3041044891, ack 1818744916, win 14600, options [mss 1460], length 0

04:56:55.080292 IP 192.168.17.80.37285 > Teltonika.lan.www: Flags [.], ack 1, win 2048, length 0

04:56:55.113096 IP 192.168.17.80.37285 > Teltonika.lan.www: Flags [P.], seq 1:74, ack 1, win 2048, length 73

04:56:55.113683 IP Teltonika.lan.www > 192.168.17.80.37285: Flags [.], ack 74, win 14600, length 0

04:56:55.247369 IP Teltonika.lan.www > 192.168.17.80.37285: Flags [P.], seq 1:37, ack 74, win 14600, length 36

04:56:55.248255 IP Teltonika.lan.www > 192.168.17.80.37285: Flags [FP.], seq 37:123, ack 74, win 14600, length 86

04:56:55.248741 IP 192.168.17.80.37285 > Teltonika.lan.www: Flags [.], ack 124, win 1926, length 0

04:56:55.618607 IP 192.168.17.80.37285 > Teltonika.lan.www: Flags [F.], seq 74, ack 124, win 2048, length 0

04:56:55.619175 IP Teltonika.lan.www > 192.168.17.80.37285: Flags [.], ack 75, win 14600, length 0

04:56:55.637545 IP 192.168.17.80.8001 > 192.168.17.255.9002: UDP, length 40

04:56:56.138416 ARP, Request who-has Teltonika.lan tell 192.168.17.80, length 46

(see second line, and last-but-one line). The frames are sent about once a second.

If I capture on the wlan0 interface, I can see no such frames.

This confirms what I had already found using Wireshark connected on the ethernet network, then on the wifi network of the RUT500.

So, why don't the UDP broadcast frames be forwarded on wifi?
by
Hi,

Wifi network and ethernet is bridged under the br-lan interface. UDP broadcast frames should be propagated on both networks, there isn’t a rule that could prevent it.

Unfortunately, your scenario is hard for me to replicate and provide you with support. RUT500 has come to an End-of-Life and Firmware 2.29 is not available our wiki to be downloaded.

Regards