I actually do have that exact problem. The only way I found how to fix it was to put the NBN router into the Optus router and then connect it to the Tenda via a LAN port. It does work. I just have no idea why 🙂
@petergdownloadThanks for your help, great suggestions, I should have thought of those. After trying a standalone cable instead of using my wall connections I was able to establish the cable is not the problem.
I pulled the connector cable out of the Sagemcom and put it into a different port and I'm now getting slow but not disastrous upload speeds. So it's either the port itself or maybe the cable had come loose but either way it's working.
@petergdownload it turns out changing ports on the Sagemcom was a temporary aberration, it turns out that setting the Tenda internet connection type to "Bridge" (the default is "DHCP") has fixed it.
I tested again this morning and found that the upload speed on the Tenda had gone back to 0. I tried changing the port used on the Sagemcom several times and one time got something other than 0 but when I tried again it was back to 0. I have 2 LAN connections in the room that has the base Tenda node and a PC as well. What I found was that any combination of cables and ports always worked correctly on the PC but the same combo would give 0 upload on the Tenda. I even tried resetting the Tenda and swapping the 2 units around and still got 0 upload so then I thought it is probably not the Sagemcom, the LAN wires or the LAN wall plugs.
As a last resort I changed the Tenda internet setting to "Bridge" and it worked perfectly and I was getting 18-20Mps upload which was way better than anything I had got temporarily. I can only guess that the Tenda set to "DHCP" somehow interferes with the Sagemcom, someone who knows more about networking may have an explanation. I had a D-Link AC1200 extender previously and I got rid of that because it was stopping the Sagemcom from working correctly as well, I tried every setting on that as well and nothing helped.