Does a Modem Affect Internet Speed?

Find out how a modem can affect internet speed.

Cable Modem Speed Kevin Jones / TechReviewer

Last Updated: September 14, 2021

Written by Brandon Jones

How the Supported DOCSIS Version Affects Internet Speed

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Newer versions of DOCSIS like DOCSIS 3.1 and the upcoming DOCSIS 4.0 allow for higher upload and download speeds than earlier DOCSIS versions.

Going from DOCSIS 3.0 to DOCSIS 3.1 will allow for up to 9 Gb/s faster download speeds and 1.8 Gb/s faster upload speeds.

The difference between DOCSIS 3.1 and DOCSIS 4.0 is minimal to most users since their internet plan from their internet service provider (ISP) often doesn't support upload speeds of over 2 Gb/s anyway.

With more implementation of DOCSIS 4.0 from ISPs, they will eventually have plans that reach higher speeds, but you won't notice a difference for now. The main difference is going from DOCSIS 3.0 and below and upgrading to DOCSIS 3.1 and above.

You will also get increased stability upgrading to DOCSIS 3.1 and above.

DOCSIS Versions - Speed Comparison
DOCSIS VersionMax DownloadMax Upload
3.0 1 Gb/s 200 Mb/s
3.1 10 Gb/s 1-2 Gb/s
4.0 10 Gb/s 6 Gb/s

Learn more about DOCSIS in my DOCSIS Cable Modem Guide and Version Comparison (TR).

Newer Modems May Have Better Firmware Support From ISP

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If you have outdated firmware on a modem, this can reduce the speed, stability of the connection, or prevent it from working altogether.

Generally, internet service providers (ISPs) push out firmware to modems, allowing them to work properly on their service. ISPs tend only to support newer modems, though and discontinue support for older models which aren't provided by the ISP.

Modems rented from an ISP are usually supported with firmware updates for longer or are swapped out for newer modems. It's typically cheaper to own a modem rather than rent one, however.

Supported Download/Upload Speeds of a Modem

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Modems can only support specific upload and download speeds, mainly based on the DOCSIS version of the modem.

The easiest ways to find which version of DOCSIS your modem supports is by: looking at the product name, looking on the bottom or side of your modem for a label, or searching online with your modem's model number.

From there, you can look at the table below and view which DOCSIS version your modem has, to find the supported speeds.

DOCSIS Versions - Speed Comparison
DOCSIS VersionMax DownloadMax Upload
1.0 40 Mb/s 10 Mb/s
1.1 40 Mb/s 10 Mb/s
2.0 40 Mb/s 30 Mb/s
3.0 1 Gb/s 200 Mb/s
3.1 10 Gb/s 1-2 Gb/s
4.0 10 Gb/s 6 Gb/s

Modem's Ethernet Port Speeds

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The Ethernet port on your modem can affect the speed of your connection because there are different Ethernet port types.

Here are the three types of Ethernet ports and their supported speeds:

Ethernet Port Type Max Speed
Fast Ethernet (10/100) 100 Mb/s (0.1 Gb/s)
Gigabit Ethernet (10/100/1000) 1,000 Mb/s (1 Gb/s)
10 Gigabit Ethernet (10/100/1000/10000) 10,000 Mb/s (10 Gb/s)

Ethernet Cable Speeds

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Even if a cable modem's Ethernet port supports a high speed, it can still be limited by the type of Ethernet cable connecting the modem and router. Lower versions of Ethernet cable can limit your internet speed because they only support specific speeds.

Here are the minimum versions of Ethernet cables that are needed to reach maximum speeds for each Ethernet port type:

Ethernet Port Type Ethernet Cable Needed for Max Speed
Fast Ethernet (10/100) Cat 5
Gigabit Ethernet (10/100/1000) Cat 5e
10 Gigabit Ethernet (10/100/1000/10000) Cat 6a

Modem/Router Combos

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Some modems are combined with a Wi-Fi router in the same device. Slow Wi-Fi speeds could affect your overall internet speed. The device's and client's supported Wi-Fi versions determine the maximum possible Wi-Fi speed.

Here are the different Wi-Fi versions, along with the expected speeds that they can reach:

Wi-Fi Version Typical Speeds Theoritical Speeds
802.11b 3-5 Mb/s 11 Mb/s
802.11a 3-32 Mb/s 6-54 Mb/s
802.11g 10-29 Mb/s 54 Mb/s
802.11n (Wi-Fi 4) 50-80 Mb/s 300-900 Mb/s
802.11ac (Wi-Fi 5) 210 Mb/s - 455 Mb/s (2x2 MIMO) 433 Mb/s - 1.7 Gb/s
802.11ax (Wi-Fi 6) 300 Mb/s - 840 Mb/s (2x2 MIMO) 10 Gb/s

Best DOCSIS 3.1 Modem

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Motorola MB8611

  • 6 Gbps max speed.

  • 2.5 Gbps Ethernet port.

  • Lightning and power surge protection.

  • Active queue management, which can reduce internet latency.

  • Backwards compatible to DOCSIS 3.0.

  • Works with Comcast Xfinity, Comcast Business, Cox Communications, and Charter Spectrum.

  • Some downsides are that it won't support future DOCSIS 4.0 service when available.

  • It does not have a built-in wireless router.

  • It does not have telephone call capability.

  • Check the latest price of the Motorola MB8611 DOCSIS 3.1 Cable Modem on Amazon (affiliate link).

    Motorola MB8611 Motorola MB8611 Check Price on Amazon (affiliate link)