Not able to connect Ethernet cable "Not connected"

The USB Ethernet adapter chipset here is the Realtek RTL8153, and some details are available here:

https://superuser.com/questions/1042661/rtl8153-driver-for-macosx

From a recent reply over there: "First: what you have is the Realtek 8153 chipset. It is known for having been finincky with macOS, and users have reported varying degrees of success over different macOS versions; sometimes a solution has involved downloading and installing new drivers from Realtek."

Based on that and from reading what was included within the linked Gist, I'd get another Ethernet adapter. This as I wouldn't expect much success from the kext path discussed. Preferably a different NIC with native support from the NIC vendor.

As for a potential alternative, there are folks that have reported the Belkin 2.5Gbps USB-C NIC works with macOS, though Belkin lists macOS on M-class and does not list macOS on Intel. I'd confirm Intel before buying, though.

ThunderBolt bridge is a connection method use when connecting a short, high-quality Thunderbolt cable between to Macs. it is Not applicable when trying to make an Ethernet connection.

Your system reports are interesting, but NOT applicable.

Ignore how it gets there and look at the ETHERNET pane.

for yours, you will want to see that some software has been loaded to support your Realtek 8153 chip based device.

if it has, you problem are likely elsewhere.

so in

system preferences > network

you should be seeing up to THREE Ethernet connections available, one for each other those devices, ALL of which appear to have drivers installed.

if not all are showing, use the ADD [+] button under the list if interfaces {wi-Fi, VPN, firewall, etc.} to ADD the interface(s), so that they can be configured.

"cable not connected" really means "I don't see no other device at the other end of the cable you provided, if any"

for the interface you want to focus on, note the "en" numbers provided in the panes you posted, you showed en5, en6, and en8. for several different devices. This may become important later.

your individual Ethernet panes were all showing M.A.C. addresses above, so I guess that means it lost track of the old one. Not sure how or why.

if it works, remember that packets going toward the Internet are sent to the TOPMOST, Working interface shown in system preferences > network.

if your favored Ethernet adapter is not TOPMOST, use the gear/[...] icon below the list, select 'set service order' and drag Ethernet to the very top the list.

Later, at the coffee shop, Ethernet will not also be Working, (no cable) so WiFi will be used instead.

Patrick Dixon wrote:

In network settings it shows red "Not connected", which I assume means it is not detecting the cable physically.

The Ethernet ports have to be turned on at both ends of the cable before you can see "Connected".

If you ran an Ethernet cable from your Mac, to, say a port on a switch/bridge/router at your workplace, you wouldn't get "Connected" unless someone in the IT Department turned that port on.

It is not clear to me how a network service connects to a physical USB-C port. How does it know which of the 4 USB-C ports is applied to the network service?

USB defines several standard device classes . There are classes covering things like keyboards, mice, drives, and network interfaces. The idea is to make a lot of things "plug and play." When you plug in your USB-C to Ethernet adapter, your Mac knows which USB-C port you are using, and it learns that a device that is of a standard device class (one associated with network devices) is plugged in.

It then creates a network service and internally associates it with the USB port. Because your network adapter is a USB-C (USB) to Ethernet adapter and not a USB-C (Thunderbolt) to Ethernet one, you see entries for the network service, and for the USB device, but not for any Thunderbolt device.

I also don't understand how the Thunderbolt Bridge works. Are the ethernet ports going through this?

No.

The Internet is a "network of networks" – and Internet Protocol was designed to run over many, many different kinds of networks. The ones that you are probably familiar with are Wi-Fi, Ethernet (RJ-45 versions), and cell phone data.

Thunderbolt Bridge is another name for IP over Thunderbolt. That is, you connect two Macs using Thunderbolt, and tell both of them to treat the Thunderbolt cable as a network link. It's the same as if you had connected an Ethernet cable from one Mac to the other - except that Thunderbolt is faster.

You're not using Thunderbolt Bridge, but the service hangs around – not configured, and not harming anything – in case you ever do decide to use it.

IP addresses used are important in debugging, But you have obscured yours. This is Not protecting your privacy.

There are two sets of non-routable IP address at play in all small networks:

self-assigned IP address are for the range 169.254.xxx.yyy. Your Mac ports give themselves an address from this range at power-up to it can be identified. This address is not Routable, meaning it NEVER goes off network, it is typically only used to talk to the Router to get a better local IP address for actual data traffic.

Private Local IP address is from one of three ranges set aside for use on local networks. They are not directly routable, but are used to send data to a Router. These are:

from Wikipedia:

https://en.wikipedia.org/wiki/Private_network

when you use addresses in any of these ranges, they are the SAME local addresses used by users everywhere. I expect half the networks in the world are using 192.168.xxx.yyy, and most of the rest are suing 10.xxx.yyy.zzz numbers.

what I need to know to help is what is your Routers LOCAL IP address from one of those ranges? and what address have you Manually assigned? and why have you NOT used DHCP address?

<< The ISP assigns the number when I connect. >>

actually, it is your own Router that assigns a good local IP address via DHCP when you connect.

your ISP DID assign an IP address for your Router, and that is the Internet-Visible address for your Router. it can be seen when you examine your Router settings inside your Router, or use

http://www.whatismyip.com/

.

This is what a Belkin USB-C Ethernet adapter shows on M1 macBook pro. looks like some variant of 8153 was still in play:

but a different vendor-name may mean there is special firmware on board that is doing things differently.

It can connect both my M1 and M2 with a Ethernet adapter made by Belkin without to much problem. The ISP assigns the number when I connect.

This is what I see ion my interface before connecting