TLDR: the Ethernet ports on the ZTE MC888 router appear to be under-powered by default causing reliability problems when using long Ethernet cables. This router is currently supplied by Three in the UK to new 5G broadband customers. Setting the WiFi Coverage to 'Long WiFi Range' (the default setting) in the ZTE control panel seems to divert some power away from the Ethernet ports resulting in random disconnections and dropped packets when using longer Ethernet cables.
Three weeks ago we moved our office from the first floor to the second floor of our building after the tenant on the second floor moved out. Coincidentally, at the same time as our move, Three sent us a new router because we got a new broadband and mobile phone deal with them. Three swapped our existing Huawei 5G router for the ZTE MC888 5G router.
Our laptops and smart phones connect to the router using WiFi, but our office printer and server are wired into an 8 port powered switch that connects to the router via a 15 metre long Ethernet cable. This allows us to keep our server and printer in a location where we want them and position the router in the best location to pickup a strong 5G signal. This setup is identical to how we had it prior to the move when using the Huawei 5G router.
After getting setup in our new office we noticed the server and printer would randomly disappear from the network. Unplugging the Ethernet cable from the ZTE router and reconnecting it would quickly bring these devices back online, but it was getting frustrating having to do this several times a day. Even when the server and printer were visible on the network, pinging either device resulted in a lot of dropped packets.
As the only equipment we changed during the move was the router, that was the first thing I suspected as faulty. I found a couple of posts on the Three support forums from other people experiencing similar problems with the Ethernet ports, but no solution. I began investigating by eliminating all the other devices as the source of the problem.
Swapping our 8 port switch for a spare didn't solve the problem. Connecting our server directly to the router (bypassing the switch entirely) didn't resolve the problem. Then I moved the server closer to the router and tried a short 1 metre long Ethernet patch cable to connect the server directly to the router. This setup worked correctly without random disconnections and lost packets. So I then wondered if our 15 metre Ethernet cable somehow got damaged during the office move.
The next thing I tried was moving the switch to next to the router and connecting our server to the switch using the 15 metre Ethernet cable and the switch to the router with the short patch cable. Again, this also worked correctly with no random disconnections and no lost packets. This told me our 15 metre cable was not damaged and that the problem only occurred when the server or switch was connected directly to an Ethernet port on the ZTE router using the long cable.
This is the point when I suspected the Ethernet port on the ZTE router might not have enough power for the 15 metre Ethernet cable. Which is odd, because 15 metres isn't excessively long, but it's exactly the kind of bizarre problem that would appear intermittently and only make itself known to a minority of customers and leave most support staff stumped.
Then I remembered seeing a setting in the ZTE control panel about the WiFi signal strength labelled 'WiFi Coverage' under the advanced WiFi settings. This was something the Huawei router didn't have. A PDF manual downloaded from the ZTE website said that setting this option to maximum meant more of the routers power went to the WiFi signal. The 'Medium Coverage' option uses 50% of the device's power consumption, but it's not clear how much the other settings use.
By default, the coverage option is set to the 'Long WiFi Coverage' (maximum power consumption) and my colleague reported getting a signal on the other side of the car park - around 100 metres away - something we couldn't do before. Changing to the lowest setting ('Short Coverage') fixed the Ethernet problem and didn't affect our office WiFi. All our devices can connect to WiFi without problem as it's a small open plan office. We now have the server and printer connected to the switch at the end of the 15 metre Ethernet cable.
