How to set the router WAN port speed? The broadband 500M speed test is only 94M. Manually change it to 1000M full duplex and it will come back.

Last month, my brother called me and told me that my family had 500M broadband and the router was a new Gigabit router. The highest speed measured by the mobile phone was 94M, not even 100M. He first suspected that the operator was cheating, and then he suspected that the router was a fake Gigabit. Finally, I went over and took a look. The optical modem was ZTE F7015T, the router was TP-LINK XDR6088, both had Gigabit ports, and the outer cover of the network cable also had CAT5E printed on it. On the surface, everything looked fine.

I entered the backend of the router and turned to the status page to find the real culprit.: The WAN port connection rate is written as 100Mbps, and the duplex is Full. In other words, this link that was supposed to run Gigabit dropped to 100 Mbit during auto-negotiation. Today I will explain this easily missed setting once and for all. If your home broadband speed test is stuck at more than 90 Mbit/s, check here first.

First distinguish: The speed test of 94M does not necessarily mean that the broadband is cutting corners. It is probably because the network port has dropped to 100M.

The broadband is 500M, the speed is 94M, and the difference in the middle is more than 400M. Many people's first reaction is that the operator did not provide enough, or the router was bought fake. However, the actual measured speed of the 500M package is generally between 470M and 500M. If it is stuck at a very round number of 90 to 94M, it is likely that a certain link is limited to 100Mbps.

Divide 100Mbps by 8 and deduct some protocol overhead, the limit is around 94M. So as long as the speed test is stable and close to 94M, don’t call customer service first, first check the WAN port speed in the background of the router. A true Gigabit link will be negotiated to be 1000Mbps, and falling to 100Mbps is the root of the problem.

There are two words here that are easy to confuse: The broadband speed is the upper limit set by the operator, and the network port speed is the actual speed negotiated between the optical modem and the router. The latter will drop from 1000M to 100M as long as one end or a section of line is not up to standard. The situation at my brother's house is that there is a problem with the network port speed, not the broadband itself.

I was also confused at the beginning. I made two phone calls to the operator and restored the router to factory settings. After a long time of trying, the network speed was still 94M. Later, I replaced the cable from the optical modem to the router, and went into the background to check the status of each port. I realized that the problem was not with the broadband, but with the slowdown of the network port itself. Therefore, this article is suitable for people who "have a lot of broadband, the equipment seems to be fine, and the speed test is over 90 Mbit/s".

When do you need to manually change the WAN port speed?

Under normal circumstances, it is enough for the WAN port speed to remain "auto-negotiation". The router will negotiate with the optical modem itself about a maximum speed supported by both parties, and you can plug it in and use it. However, in the following four situations, automatic negotiation will drop out of the chain, and only then do you need to specify manually.

The first type, the network cable looks like it has eight cores, but the actual crystal head only presses four cores. Ideally, a four-core cable can only run 100M. If you plug it into a Gigabit port, the router will still recognize it, but the speed will be locked to 100Mbps. In the second type, the optical modem only has a 100M port plugged into it. Like the ZTE F7015T, there are several network ports on the back. The IPTV port and some old ports are 100M. If the broadband dial-up is not plugged into the Gigabit port, the WAN port will naturally only have 100M. I will write down the method of judging this matter in How to distinguish between Telecom optical modem Gigabit port and 100M port inside.

The third type is that the network card or network port is damaged by static electricity, or the negotiation is abnormal after being hot-swapped for a long time. Obviously the device and cable support Gigabit, but it only gives you 100M. I once encountered a computer network card that automatically downgraded to 100 Mbit/s, and then I found it after searching in sequence. The details are in The internet speed drops to 93 Mbit/s and no problem can be found In this article. The fourth type is that the negotiation modes at both ends are incompatible, especially if the old router and the new optical modem are mixed, or an old switch is added in the middle, the negotiation will occasionally break down.

One word of judgment method: First look at the router status page. The WAN port rate shows 100Mbps, and then check along the lines. Make sure that the optical modem port, network cable, and crystal head are all fine before manually changing it. Don't force it to run Gigabit as soon as you start it.

Where is the background changed?: There are two paths, TP-LINK and Mercury, both under Internet settings.

The path of my brother's TP-LINK XDR6088 is like this: Go to the backend of the router on your mobile phone or computer, click "Routing Settings", then click "Internet Settings", scroll down on the broadband dial-up page, and find "Advanced Settings", where there are two drop-down boxes for "WAN Port Speed" and "WAN Port Duplex Mode".

The position of old backends such as Mercury D191G is similar.: Enter 192.168.0.1 , click "Routing Settings" → "Internet Settings", there is WAN port speed in the advanced options on the right. Different firmware will write it as "WAN port connection mode", "Ethernet speed" or "port speed", but the meaning is the same. If you can't find it, just browse through the menus of System Tools, Network Settings, and Advanced Settings, and it's almost the same.

Before changing it, I recommend taking a screenshot or writing down the original value. If you cannot connect to the Internet after manually specifying it, you can still change it back to automatic negotiation. This habit of "leave a way out before changing" is the same as other router settings. I checked it last time. Router settings changed but not effective , half of the problems lie in not confirming the old value.

Another point is that the WAN port speed and the LAN port speed are two different places. You only change the WAN port. The computers and TVs plugged into the LAN port of the router use the LAN port. If 100M is also dropped there, the speed test will still only be 94M. So in the end you have to look at both the WAN and LAN ends.

How to choose among the four options: 1000M full duplex cannot be accessed with your eyes closed.

There are usually four gears in manual settings. I use a table to explain them clearly. Don’t make a blind choice when you see 1000M.

Full-duplex means sending and receiving at the same time, while half-duplex means only going in one direction at the same time. Nowadays, almost all household equipment supports full-duplex, so half-duplex can basically be ignored. What really changes is the first two lines: There is no problem with the line. If you want to force it to run full, choose 1000Mbps full duplex. ； The line indeed only supports 100Mbps, so just choose 100Mbps full-duplex and wait for the line to be changed before upgrading.

My brother's family finally chose 1000Mbps full-duplex. After saving, the router automatically restarted the network. The WAN port status page quickly changed to 1000Mbps. The speed of the mobile phone was directly measured to 478M. He thought I had changed the machine.

Two pitfalls I have stepped on: After changing it, the network was disconnected, and after changing it back to automatic, it dropped to 100Mbps again.

The first time I helped someone change it, I chose 1000M full-duplex. After saving, the WAN port of the router directly showed that it was not connected. After a long search, I found out that the outer cover of the cable inside the wall in his house was written CAT5E, but the crystal head was a four-core one that the decorator had installed to save trouble. After the equipment on both ends was forced to Gigabit, we couldn't agree on it. In this case, it's not that the router is bad, it's that the lines are not cooperating. I replaced the network cable with a ready-made eight-core cable, and auto-negotiation also ran Gigabit reliably.

The second time was at a colleague's house. It automatically negotiated 1000M today and dropped 100M tomorrow. Manually changing it to 1000M full-duplex was stable, but every few days the network cable broke when touched. In the end, I had to replace a new jumper to completely solve the problem. So my experience is: Manual specification can provide temporary relief, but if the cable or crystal head itself is not working, don't expect the settings to cover it up. Changing the cable is the ultimate cure.

By the way, let’s take a look at the WAN port and LAN port.: The cable coming out of the optical modem must be plugged into the WAN port of the router. If it is plugged into the wrong LAN port, the backend WAN port speed is no longer correct and there is no network connection. The difference between this gap, I specifically focus on What is the difference between the WAN port and the LAN port of the router? I have drawn pictures in it, you can take a look at it if you are installing it for the first time.

How to verify after modification: Look at the status page, don’t just rely on the speed test numbers

After saving the settings, don’t rush to close the background. First check the WAN port status page to see if the speed is 1000Mbps and the duplex is Full. This step is more direct than measuring the speed. Confirm that the link is Gigabit, and then turn on the mobile phone or computer to measure the speed.

To test the speed, I recommend plugging a computer into the LAN port of the router to test the wired speed, rather than using WiFi. Because WiFi partitions, dual-band integration, and terminal network cards will suppress the results. If you measure 300M and think it is because the WAN port has not been changed, in fact, the wired connection is fine and the wireless one is lagging behind. The sequence and pitfalls of the wired speed test at my home are summarized in Gigabit broadband speed test is only over 200 megabits Here, you can exclude them as follows.

If the WAN port is already 1000M and the computer cable is still only 94M, then continue to check the computer network card and LAN port speed, and don’t look back and doubt the operator. On the other hand, if the WAN port displays 100M and it fails after manually changing it to 1000M, follow the sequence of "Change the line - Change the port - Change the settings again". Do not try hard back and forth.

Finally, this setup is summarized into four steps:: First check the status page to confirm that 100M is off, then check the optical modem port and eight-core network cable, then manually select 1000M full-duplex for emergency, and finally test the wired and review the WAN port status. According to this sequence, 90% of broadband stuck at 94M can be recovered by yourself.