Head-to-head · Best Standalone DOCSIS 3.1 Cable Modems

Motorola MB7621 vs Motorola MB8611

Which is the better buy? Side-by-side on rating, price, strengths, and watch-outs — with the published ratings we averaged to get there.

Verdict is reader-supported. As an Amazon Associate we earn from qualifying purchases. Some links on this page are affiliate links — if you click through and buy, we may earn a small commission at no extra cost to you. Our ratings are sourced from independent publications, not sponsors.

The short answer

Motorola MB8611 comes out ahead by a narrow margin (4.0 vs 4.2). The gap is mostly about high-speed wired connection users willing to accept firmware risks — read the strengths below before deciding.

Ranked #5 in Best Standalone DOCSIS 3.1 Cable Modems

Motorola MB7621

4.0

3 sourcesall derived$72as of Jul 31

The Motorola MB7621 is a DOCSIS 3.0 cable modem that performs reliably on the right ISP, holding 500 to 900 Mbps with stable connections and running cooler than some competitors. It isn't suitable for plans above 700 Mbps, and its days are numbered: Spectrum plans to end support by October 2026. Wirecutter named it 'the best modem for most people' back in 2019, but those limitations make it a temporary fix for anyone who expects to upgrade.

Strengths

— Operates on DOCSIS 3.0 with 24 downstream and 8 upstream channel bonding
— Runs on a Broadcom chipset that runs cooler than some rivals
— Provides stable connection in the right ISP environment with speeds between 500 and 900 Mbps

Watch-outs

— Not suitable for plans above 700 Mbps due to DOCSIS 3.0 protocol ceiling
— Spectrum is ending support for DOCSIS 3.0 modems on October 28, 2026

$72 · Check Price on Amazon Full review →

Higher ratedRanked #3 in Best Standalone DOCSIS 3.1 Cable Modems

Motorola MB8611

4.2

1 sourceall derived

The Motorola MB8611 is a DOCSIS 3.1 modem with a 2.5Gbps Ethernet port and support for up to 32 downstream and 8 upstream channels. Tech Reviews called it a great modem, pointing to its backward compatibility and AQM for low-latency performance. Firmware is the weak spot: users have reported stability problems, particularly on version 21.3.7, and one switched to an Arris S34 after prolonged trouble. It's approved for Comcast Xfinity, Cox, and Spectrum. Choose it for fast internet, not if you need voice capabilities or can't tolerate firmware instability.

Strengths

— 2.5Gbps Ethernet port for high-speed wired connections
— Fast DOCSIS 3.1 speeds with support for 32 downstream and 8 upstream channels
— Backward compatible with DOCSIS 3.0

Watch-outs

— No voice capabilities
— Has firmware issues reported by some users (specifically 21.3.7 firmware causing instability)

Check Price on Amazon Full review →

Derived means the reviewer published no score, so one was inferred from their written verdict. Everything else is a number the publisher printed. How we rank.

How they stack up

Motorola MB7621

The Motorola MB7621 is limited to DOCSIS 3.0 speeds, unlike the Arris SB8200 which supports DOCSIS 3.1, but it runs cooler than the Motorola MB8600. Unlike the Netgear CM1000, it doesn't support Gigabit speeds and is not future-proof, and unlike the Motorola MB8611, it lacks 2.5Gbps Ethernet support.

Motorola MB8611

The Motorola MB8611 supports 2.5Gbps Ethernet, unlike the Arris SB8200 which is capped at 1Gbps, but it's prone to firmware issues compared to the Netgear CM1000 which offers more stable performance. Unlike the Motorola MB8600, it doesn't support 6Gbps WAN speeds, and unlike the Arris SBG8000, it lacks integrated Wi-Fi.

Specs side-by-side

Spec	Motorola MB7621	Motorola MB8611
Docsis Version	DOCSIS 3.0	3.1
Max Download Speed	500-900 Mbps	2,500 Mbps
Downstream Channels	24	32
Upstream Channels	8	8
Dimensions	7.25"L x 2.25"W x 7.88"H	7.25"L x 2.25"W x 7.88"H

← See the full ranking of best standalone docsis 3.1 cable modems