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2020 iMac 5k - 10G ethernet not working

I've recently started to want to use my WIRED ethernet on my 2020 iMac 5k. for the past 4+ years, I've been just fine with wireless, but I've decided to updated/upgrade my home intranet (hardware), updating my switch from an 8 port gb switch (unmanaged) to a 16 port 2.5gb switch (unmanaged), and all my cat5/5e/6 cabling to cat8 braided. I also updated my wifi/router from an service provider/OEM single/standalone modem/router to a wifi7 quad frequency 3 node mesh system.


I'm finding that with both my old network, and my new network setup, I cannot get the iMac 5k wired ethernet to properly work.


hardware tests all show the 10g ethernet is functioning properly. terminal ifconfig en0 shows it properly negoationed (after reboot), an IP address in the correct range by the router, as well as the 2.5gb limit of the switch. the old switch hardware also produced similar results ... a 1gb limit auto-negotiated as shown w/ifconfig en0. The network (again) after a reboot), shows the Ethernet Connection as "active" (green). within the Router software, I see that connection as OFFLINE (so somebody's lying).


if I deactivate the ethernet, then reactivate it, network will ALWAYS go to self-assigned IP (orange color) with a 169.x.x.x address. Only a reboot of the iMac will get the network connection back to Green/Active.


I've tried changing the service order (when it's first, no internet/intranet works). When WiFi is first, everything internet/intranet works.


I've tried deleting then re-adding the service back multiple times.


I've tried setting a static IP (manual) making sure on the router that IP isn't being used.


I've tried inactivating the network Wifi and just using (when green) the active 10g ethernet.


I'm privy to many of the google searches regarding this issue, and frustrations others have expressed on this forum, macrumors, and other forums.


This 10G ethernet should be plug and play.


I will (in a couple weeks) have access to a windows 10g ethernet laptop ... will update this post with the testing results ... I'll test using the same cable/connection to see if there's any issues / problems with this (this will rule out my network as the culprit, which I'm absolutely sure isn't the problem given I've tested on a brand new network/setup).


Tried some things like no VPN (deleted), privacy turned off, etc. I guess I could install the originally provided OS to see if it works ... maybe some weekend when time permits ...


MacOS 15.1

2020 iMac 5k / 128gb / 8tb


I'll be updating w/more testing and images as I proceed through this issue

iMac 27″, macOS 15.1

Posted on Nov 9, 2024 5:03 AM

Reply
15 replies

Nov 17, 2024 7:07 AM in response to hcsitas

hcsitas wrote:

Quite a chop suey mix. How about a picture?

The mesh router is the most-likely culprit IMO. It’ll probably work without - swap it with something less exotic (at least for troubleshooting). Or see if it’ll work minus all the switch-wall-cat-cable-jazz i.e. direct-connect (probably will).


Yeah; a description of the network would be goodness; what’s where, for the major pieces. I’d hope the switch is directly off the core router (and the core router is presumably also DHCP server), and not dangling off the mesh somewhere else, for instance.

Nov 11, 2024 3:54 AM in response to dialabrain

my ISP is Verizon 5g home internet ... speeds capped at 100/5 ... but the ISP is not in play here as its set to passthrough to my deco be95 mesh system ... and I've tested legacy routers as well ... same situation ... in fact, I've tested with a DECO XP75 Pro mesh system, a ASUS BE33000 mesh, and the Verizon provided modem/router ... all behavior is the same ... so I think we can rule out the router and router/modem as the issue

Nov 17, 2024 6:27 AM in response to TJF@DENVER

If you’re getting self-assigned, your DHCP is not playing well, or your host is badly botching the request, or you’re not getting to the DHCP server.


Given your report, there should be differences between the working and non-working states, for whichever en* device you’re using:

ipconfig getpacket en0


Check switch firmware and update, and check the DHCP server logs, too.


That static with a designated router also fails is not an auspicious sign; that’s either the host IP stack gone bad, or problems with the cabling, the switch, or the router.


Not having visibility into the switch port makes this more difficult too, unfortunately. Does your unmanaged switch have link speed indicators on the port? That might provide some clue when working or not-working.


Yeah, install macOS on an external, boot that, and see if that works.


Your planned other 10 GbE client test is also a good one.


Does physically un-plugging and re-plugging the patch cable clear the self-assigned wedge?

Nov 18, 2024 6:37 AM in response to TJF@DENVER

Thank you to all that responded.


I remembered I had a 2012 MBP Retina and a TB to Ethernet Dongle/Adapter ... I took that same Cat8 connection from the 2020 iMac that failed to give me connection, plugged it into my 2012 MBPr ... and it worked immediately ... I think its reasonable to rule out anything from that CABLE on through my network ... this appears to be ONLY isolated to the 2020 iMac's 10G ethernet not working.

Nov 18, 2024 7:23 AM in response to TJF@DENVER

The Ethernet dongle isn’t the real thing, IMO n/a. Additionally, it looks like you’re pumping too much traffic through the solo 5G Verizon wireless which is susceptible to things beyond your control, and the highly-spec’ed and marketed but otherwise untested and unverified TP-Link box which also appears overloaded with traffic.


The only way to isolate your Mac from all these variables is to test on an internal network with real 10G ports all the way, using direct-connect short cables on both sides (and without anything else except a non-exotic router connected).


In other words, remove the Verizon + TP-Link Chop Suey from your picture and test with only the switch, suitable non-exotic router, Mac and another 10G device that can receive and send files. Until that happens, the Mac IMO is not suspect, an amused spectator at best.


Reinstalling MacOS is an essentially hail-Mary pass, nevertheless worth a shot given you’re already out of timeouts. That said, I seriously doubt it’ll make any difference.


Good luck! I’m outta here 👋

Nov 18, 2024 9:24 AM in response to TJF@DENVER

Absent some debugging luck, or maybe some missed setup step, I don’t know that this is going to get sorted here. What you have should work, but without a view into the switchport?


No 16-port 2.5 GbE / 10 GbE switch is listed at the NICGIGA vendor’s website, so details on that are unclear. The NICGIGA unmanaged switches don’t seem to have firmware, either.


For those following along at home and (like me) unfamiliar with NICGIGA…


Here’s a review of what seems closest (albeit 8 ports and POE): https://www.servethehome.com/nicgiga-s25-0802p-8-port-2-5gbe-and-2-port-10g-poe-switch-review/


Here is an aggregate listing and review of the lowest-cost 2.5 GbE switches: https://www.servethehome.com/the-ultimate-cheap-2-5gbe-switch-mega-round-up-qnap-netgear-hasivo-mokerlink-trendnet-zyxel-tp-link/


Looks like NICGIGA, VIMIN, and ienRon (and probably some AliExpress offers) all share common sources for at least some of their products, too.


As for the mesh part of this (and that’s very likely involved here as that looks to be the local DHCP server), the TP-Link DECO BE95 mesh router does have firmware, and there is an update from June 2024. Is that firmware loaded?


I don’t have an analog to this configuration though, as the 2.5 GbE switching gear I have access to is mid-range and managed and all from the same vendor as the mesh, firewall, DHCP server, and related.

2020 iMac 5k - 10G ethernet not working

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