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RCN's website has a document that states: 'most routers will slow down to the speed of your slowest device' (link, FAQ #1). Assuming this is true, how does a home user figure out whether and which device is slowing down the router (or whether the router itself is to blame for slower-than-advertised speeds)?

Given a generic network setup:

  1. Connection from wall (e.g., Cable, Fiber, DSL) with some promised speed (e.g., 25Mbps down, 5Mbps up), connected via coax, fiber, or phone line to
  2. Modem (or ONT), connected via ethernet cable (Cat 5e) to
  3. Wi-Fi Router, connected via ethernet cable (Cat 5e) or Wi-Fi to
  4. Device(s) - e.g., phone, smart speaker, TV, printer, game system, security cam, etc.

There are three connections that matter:

  1. ISP to modem
  2. modem to router
  3. router to device(s)

ISP to Modem Test:
Test the modem's wired speed by connecting a laptop directly to the modem via ethernet cable (good luck finding a laptop that still has an ethernet port! If connecting via usb-ethernet dongle, may be dependent on USB port or dongle speeds.). Run internet speed tests on the wired modem connection. Call this speed 1.

Modem to Router (Wired) Test:
Test the router's wired speed by connecting a laptop directly to the router via ethernet, and router to modem via ethernet cable. Run internet speed tests on the wired router connection (max = speed 1). Call this speed 2. If speed 2 is a lot slower than speed 1, then the router is to blame?

Router to Device (Wi-Fi) Test:
Finally, test the connection speed of a device that is wirelessly connected to the router (max = lower of speeds 1 and 2). Call this speed 3. If speed 1 and 2 are basically the same, and speed 3 is a lot slower than speed 2, then either the router's wifi or the device is to blame? Some devices you can't check directly (e.g., how do you test a printer, tv, or smart speaker's connection speed?) The best I can think of is testing the speed of a laptop connected to the network while the other device (printer, tv, speaker) is connected?

Other Tests:
Switch which device is wirelessly connected to the router and re-test.
Switch a wireless device (e.g., printer) to wired connection and re-test.
Turn off all the Wi-Fi devices and then only connect one at a time to the network and test speeds. e.g., laptop + phone 1, laptop + speaker, laptop + printer, etc. (is this even worth the effort?)

Is there a programmatic way to test the connection speed of each of the devices that are connected to the router?

Is there some way to figure out whether your wireless router is limited to slower speeds and that upgrading to a different router would result in faster speeds, without going out and buying a new router, installing it, activating it (typically a lengthy and time-consuming ISP phone call), and speed testing it?

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  • I must point out that the premise is false. It's a huge myth. Wireless routers speak to each client using the fastest scheme that both the router and that particular client support, even if other clients on the network don't support those modern speedups. The only problem (the kernel of truth behind the myth) is that old slow clients need a lot more airtime to move the same amount of traffic, so an active old client can take a big slice of the airtime pie unless the router supports "airtime fairness".
    – Spiff
    Commented Aug 21, 2019 at 21:44
  • Yes the premise is false. The most common problem that causes a wireless network to operate below its optimal speed when it's within reasonable range is actually interference from neighboring wireless networks, and other devices sharing the same frequency. Networks need to be either on the same channel or spaced 4 channels apart to not interfere.
    – Alex Cannon
    Commented Aug 27, 2019 at 19:45
  • Routers have improved since I wrote this question. Admin interfaces of newer ones often display TX/RX rate, channel, SSID, etc. of each device. If extenders/mesh are used, then this interface may also show which one (main router, extender 1, etc.) each device is using to connect, and the strength of connection to extenders/satellites. I have found this information to be quite helpful in diagnosing poor connectivity of individual devices, poor placement of satellites, which devices should use wired connections, and routers with poor automatic device speed optimization algorithms.
    – Brian D
    Commented Dec 6, 2021 at 21:55
  • My go to answer these days: slow internet on any device? restart the router.
    – Brian D
    Commented Dec 1, 2023 at 18:08

1 Answer 1

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First, device speeds can be found on the web.

Second, the way to find out if a particular device is slowing the router is to measure speed from a fast PC with all other devices disconnected, including cameras, thermostats and other IoT devices. Then reconnect them, a few at a time (or in a binary search), and remeasure speed to see if it drops.

BTW, what happens if a device is intrinsically capable of high WiFi speed, but is near RF interference or is far from the router and gets a poor signal? Though data rate would drop, would that slow other connections?

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