Upgraded to 400 Mbps, Internet download speed on router is less than 120 Mbps

PGhPGh Posts: 5 ✭✭
edited September 20 in Connectivity Sep 20, 2020

My internet was upgrade to 400 Mbps. While trouble shooting, if PC is directly connected to the model, the download test got the full speed(bandwidth). However, if PC is connected to Router, the download speed is less than 120 Mbps. (I'm using Spectrum speed test.)

Router has 4 ports. All 4 ports have the similar result ~120 Mbps.

Is there any limitation between the modem and the router? Does really Spectrum support 400 Mbps from the router? Is there any solution for this?


  • karlbeckmankarlbeckman Posts: 2,228 ✭✭✭✭
    Sep 21, 2020

    It sounds like your router is not capable of delivering the 400 Mbps tier of service coming from your router. Does your router have Gigabit ethernet ports? Does your PC have a full Gigabit ethernet adaptor port? Or are they only capable of running at 100 Mbps like your previous modem? And, as you have noticed, WiFi data transfer speeds can often be limited to less than that of the wired connection ports using an ethernet cable.

  • PGhPGh Posts: 5 ✭✭
    Sep 21, 2020

    I got new devices, a modem and a router, from Spectrum service center. So, it was assumed that these are the latest equipment. When my PC is connected to either modem or router, it shows as 1 Gbps. So speed detection is not a issue. One possibility is there is provisioning of ethernet ports on router. Otherwise, it is hard to understand. Is there any possibility that router is limiting ~100Mbps on Ethernet ports?

  • misterjmisterj Posts: 118 ✭✭✭✭
    Sep 21, 2020

    PGh, there is no provisioning of your router. Have you tried fresh/new Cat 5E Ethernet cables or higher (6 or 7)? How long are the cables? Please tell us what router you have. If it is from Spectrum, please go get another and try it. If you have a router of your own or a friend, try it. Your modem will easily run 1000 Mbps. If it had the right Ethernet output port, it could run 5 Gbps if the ISP offered it. Thanks and enjoy, John.

  • PGhPGh Posts: 5 ✭✭
    Sep 21, 2020

    Dear misterj,

    I got a Modem and a Router so it was assumed that they are the latest ones. When my PC is connected to the either Modem or Router, device managers shows that it is 1 Gbps.

    When my PC with the same cable is directly connected to Modem (with Spectrum assistant), the download speed reached >400 Mbps. This implies that no problem to the modem, also no problem of my PC connection. However when the same PC and the same cable is moved to an Ethernet port of router the speed of download drops to ~ 100 Mbps.

  • misterjmisterj Posts: 118 ✭✭✭✭
    Sep 21, 2020

    PGh, look at the Adapter setting for current speed:

    If you are measuring all four ports at the same time, then your results are about right. Thanks and enjoy, John.

  • PGhPGh Posts: 5 ✭✭
    Sep 21, 2020


    It is 1 Gbps. With one PC, there is no chance to test all 4 ports at the same time. If modem is supporting ~ 400 Mbps, and there is 1 Gbps connection between the modem and the router, also my PC shows 1Gbps connection to the router, the throughput should be close to 400 Mbps, not 100 Mbps.

  • RAIST5150RAIST5150 Posts: 835 ✭✭✭✭
    Sep 21, 2020


    Have you tried resetting the router to defaults yet?

    It could have restrictive QoS rules in place... hardware acceleration disabled... who knows what state it may have been left in from the last user.

  • PGhPGh Posts: 5 ✭✭
    Sep 21, 2020

    @RAIST5150 ,

    Thanks for your reply.

    I had worked with Spectrum technical support via phone for one and half hour, Modem was rest, Router was reset, even power cycled both of them. That did not help. I'm expecting to have Spectrum field technician to measure actual bandwidth between my PC and an Ethernet port of router.

  • RunsWithScissorsRunsWithScissors Posts: 1
    edited September 21 Sep 21, 2020

    We're going off the rails here.

    The screen snapshot directly above only shows the **CAPACITY** of the NIC adapter in the PC. It is telling you that the Aquantia 10 Gbps installed in the PC can handle a speed of 1.0 Gbps, but the screen shot contains zero information as to the actual data rate being sent from the router to the Aquantia 10 Gbps NIC.

    Put it this way. If you disconnected your PC from the network by unplugging the ethernet connection, the Aquantia 10 Gbps NIC status would still show 1.0 Gbps.

    The best way to truly test the actual speed of your network is by running an internet speed test. Use speedtest.net. I would not recommend using the speed test found in the Internet section of the Spectrum website, mostly because I don't trust Spectrum. If you contracted for 400 Mbps service, you should be able to come fairly close to that number, probably somewhere between 325 Mbps to 375 Mbps, provided you are hardwired between router and PC.

    If you're using a Wifi connection, you'll be limited to the maximum speed of your Wifi adapter installed in your computer.

    To the OP:

    Your router should be capable of 1 Gbps out of the 4 LAN ports. 1 Gbps ethernet has been pretty much standard equipment on all routers for nearly a decade. But it's always a good idea to check. Look at the manual and read the specs. If you don't have a manual, google the model name and number on the web and look for either a manual or the spec sheet. If you feel that the equipment is indeed new (as opposed to reconditioned), then you should be able to get 1 Gbps out of your new router.

    IMO, It comes down to 2 different things. You need two (2) Cat 5e or better cables, one between the modem and the router, the other between the router and the PC.

    If that doesn't work, hard reset the router and check if a firmware upgrade is needed. Spectrum loves to reuse old equipment. Unless you witnessed the tech taking the router out of a new box, don't assume that your router is brand new and unused.

    If that doesn't work, you need a new router. Spectrum often uses the cheapest, lowest bidding Chinese contractors to manufacture their modems, routers, and cable TV boxes, so the defect rates of their equipment is higher than the equipment we would buy through normal U.S. consumer channels. Spectrum's equipment often fail right out of the box.

    If there is no Spectrum office close by to do an exchange and you can't wait for a Spectrum tech to come to your house to make the swap, then go to Costco, buy a new router and return it when you finally get your replacement Spectrum router.

  • misterjmisterj Posts: 118 ✭✭✭✭
    Sep 21, 2020

    PGh, we have not gone off the rails here. The screenshot shows the current connection capability. I wanted to make sure it did not say 100 Mbps - consequence of a bad cable/connector or router. It is clearly not **CAPACITY** which is 10.0 Gbps for this NIC. It is not the speed. Since your router is wireless, then you could have any number of wireless users using up you download speed. You could turn off both radios in your router, Good luck and enjoy, John.

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