MacBook Pro M3 Max can't get ethernet to go above 1Gb

That MacBook Pro does not have a built-in Ethernet port.

You say that the adapters you have tried support 2.5 Gb Ethernet speeds. What other speeds do they support? What speeds does your Internet Service Provider support? Is there a speed above 1 Gigabit Ethernet that both your adapters and the ISP's equipment have in common?

Osprey wrote:

 Thank you for your reply. Yes the MBP does not have ethernet port so am using a 2.4Gb ethernet to thunderbolt 4 adapter. I don't know what other speeds it supports but I did some digging on the internet which suggests it can do 1.6Gb. The ISP goes up to 1.6Gb and they verified that the modem is actually supplying 1.6Gb to the premises. They swapped out the router in case that was the problem but the new one is exactly the same as the old. Any advice appreciated thank you.

I could be mistaken, but I've never heard of 1.6 Gigabit Ethernet. Your ISP may be supplying data at a rate of "up to 1.6 Gigabits per second", but what is the actual speed of the Ethernet port (on the LAN side) that they use for doing that?

My guess is that the port will be capable of some mixture of 1, 2.5, 5, and 10 Gbps Ethernet. Let's say that their port can run at 1 or 10 Gigabit speeds, and your adapter can run at 1 or 2.5 Gigabit speeds. Then, even though both can run faster then 1.6 Gigabits per second, the lowest common denominator will be Gigabit Ethernet.

Osprey wrote:

This one among others including a belkin

https://www.amazon.co.uk/Plugable-Ethernet-Adapter-Compatible-Thunderbolt/dp/B084L4JL9K/ref=mp_s_a_1_3?adgrpid=117311117986&hvadid=606281783682&hvdev=m&hvlocphy=9045470&hvnetw=g&hvqmt=e&hvrand=14872500515066242885&hvtargid=kwd-316089288463&hydadcr=5240_2344874&keywords=plugable+ethernet+adapter&qid=1702716772&sr=8-3

The description of that Plugable USBC-E2500 adapter says that it connects at 10/100/1000/2500 Mbps speeds. Also that you might need to install a driver on macOS to get some "core functions" to work correctly.

"Drivers built into Windows 11, 10, 8.x, and 7 as well as macOS 10.7 and above (driver install required for 2.5Gbps link rate and jumbo frames), and Linux kernel 3.2 and above."

I'm thinking that Mac OS X 10.7 (Lion) is quite old, and Intel-only.

An Intel-only kernel extension written for Lion would not run on an Apple Silicon Mac. Rosetta 2 can only translate user-land code (application code) – not code that runs at system level, like kernel extensions.

I went looking on the Plugable site to see if I could find out more about drivers, and found this:

https://plugable.com/products/usbc-e2500

https://plugable.com/pages/wired-ethernet-network-adapters-drivers

According to this, you don't need a driver for macOS 11.x (Big Sur) through 14.x (Sonoma) – but there are "some minor issues."

https://plugable.com/products/usbc-e2500#nav-get-started

• "macOS (11.x+): No driver install available, use built-in NCM driver. Note: There are known issues with incorrect link rate reporting and packet counts on macOS 11.x+ With auto-negotiation, the adapter will get a 2.5Gbps connection, and the device operates normally, but it will appear in macOS that the link rate is only 1000Mbps. Jumbo frames are not currently supported on macOS 11.x+. We are working with Realtek on drivers to resolve these issues"

Have you tried testing the speed of your Internet connection, with Ookla Speediest, or something like that? Maybe you are actually getting 1 Gbps speeds, but your Mac is just reporting 1 Gbps as the link rate because of this (Plugable? Apple?) bug.

Do you have a Wi-Fi 6E (6 GHz) 802.11ax rated router? Depending on your environment and interference, you still might obtain 1.6 - 2.0 Gbps connection between the M3 Max and the router.

If you have a 1 Gb rated switch anywhere between the router and your Mac, there is your bottleneck. My cable modem, router, and Startech switch are all rated for 2.5 Gb Ethernet, and I use Cat 5E or 7 cabling.

It is really great that your ISP is providing up to 1.6 Gigabits/sec data rate.

To transport that high data rate around your network without slowdowns you need standard links, running at standard speeds. So you would like something above 1 Gigabit/sec, such as 2.5 Gigabit/sec.

What Make&Model adapter are you connecting?

I suggested Wi-Fi 6E to avoid spending more hours on this problem when you could achieve comparable bandwidth (to your router) using a 6GHz SSID. Sometimes focus excludes all other possibilities and the engineering problem is not solved using simpler methods.

Sorry for this reply a little late to the party.

I use this USB-C to 2.5Gb/s Ethernet adapter which works flawlessly on an Intel Macbook Air or on a M3 Pro Macbook Pro.

https://www.amazon.com/Cable-Matters-Gigabit-Ethernet-Supporting/dp/B0844WPD3W/

It is now discontinued, but newer products such as this one should work just as well.

https://www.cablematters.com/pc-1286-125-usb-c-to-25-gigabit-ethernet-adapter.aspx

However, please bear in mind that the problem may come from the router side, since not all 10GBASE-T Ethernet devices support slower 2.5GBASE-T.

<< mystified as to why I am not getting the full speed. >>

what device are you connecting the MacBook Pro to?

Does that other device support ANY speeds above 1 G bits/sec? For example, the "best" Verizon FIOS Router does NOT support any speeds above 1 G bit/sec.

What Make&Model adapter are you using to make the connection?