Powerline adaptor and multicast

Installing and Using OpenWrt Network and Wireless Configuration
1

Hello,

I have installed OpenWRT on my Powerline adaptor (TL-WPA8630P) as an attempt to solve some multicast issues I was having with the stock firmware. However, after further investigation I realised I have no idea what the issue really is… (I was hoping I just need to enable IGMP snooping).

First here's a quick overview of my network:
• I have broadband router from my ISP doing DHCP
• Attached to one if it's ports is the Powerline adaptor connecting to a room outside the range of the broadband router WiFi
• OpenWRT is installed on the Powerline adaptor and configured as a bridge. Wired and wireless clients connected here still get an IP from the broadband router.

The problem is with multicast, specifically with CoAP which uses 224.0.1.187 and UDP on port 5683.

On each side of the Powerline I can subscribe/send/receive packets on this multicast address between wired, wireless and wired/wireless clients. However these packets never traverse the Powerline.

Initially I though the issue was will all multicast traffic, but then I noticed that Bonjour is working fine. I have a Mac mini on one side of the Powerline that I can see just fine on the other side… So it's not all multicast traffic being blocked?

I then tried a simple multicast test on another address using iperf. I setup a listener with:

$ iperf -s -u -B 224.1.1.1 -I 1

and a producer with

$ iperf -c 224.1.1.1 -u -T 32 -t 3 -i 1

If both listener and producer are on the same side of the powerline everything is fine. If they are on each side I can't see any packets.

So why is Bonjour multicast working but any other multicast isn't? Is there something I can do on OpenWRT to forcefully allow multicast in this scenario?

2

I've updated the firmware on the plc side using the tpplc from TP-Link and I think the issue is fixed. At least I'm seeing some packets cross the power line. Need to test a bit more.

3

I have the 8630p too and I'm curious which firmware you've found. I guess you're not using a full, official firmware from tp-link, right?

4

So, apparently, there's two parts to these devices, the firmware that controls the routing (which I've now replaced with OpenWRT), and the firmware that controls the Powerline stuff (ie, actually sending the signal to the wires).

I believe I actually updated the firmware for the other end of the Powerline network (the one that has just a single ethernet port and no wifi). That can only be done with their software.

Anyway, I'm currently not so sure that was the fix. Since the Mac I was using to test the multicast had some complex routing rules (a bunch of interfaces for virtual box, internet sharing, and just cruft left behind from various tests). While I was trying to update the firmware I was also cleaning this up and, looking back, this might have actually been the fix.

5

Thanks for the link. It looks like the firmware from 2020 is only available on the Portuguese site.. For other countries the latest version is from 2017.

I have no big problems with my 8630p, but it's good to know there's something newer to try if I run into problems with the powerline functionality. Thanks!