Ethernet link emac rx dma stuck (reboot loop)

New community member here:

Had a Mimosa 5Bc pair installed a few days ago. One of the units is on a 100 meter long CAT7 cable powered by the Mimosa 56V/0.93A 10/100/1000 POE injector. This unit is exhibiting unfortunate behaviour that manifests in two ways:

a) on boot only a 100 Mbits/s Ethernet link is negotiated;

2020-05-19 16:18:32 (UTC +0000) root: MIMO_EVENT binaryversion=90afb59714e83b80041e9bf58c3ba9765029cc29 build_time=2020-04-17 12:05:52 (UTC +0000) bamboo_build_time_stamp=2020-04-17T12:04:30.354Z bamboo_build_number=28 project=FWREL-REL6 branch=release/1.5.2
2020-05-19 16:18:39 (UTC +0000) root: MIMO_EVENT ethernet vendor id: 0x221622.
2020-05-19 16:18:41 (UTC +0000) root: MIMO_EVENT Startup reason: Power On Reset
2020-05-19 16:18:46 (UTC +0000) root: MIMO_EVENT ethernet link up (100/Full)
2020-05-19 16:18:54 (UTC +0000) root: MIMO_EVENT ethernet link emac rx dma stuck

b) usually a reboot cycle follows with messages like these in the logs:

2020-05-19 16:20:21 (UTC +0000) root: MIMO_EVENT binaryversion=90afb59714e83b80041e9bf58c3ba9765029cc29 build_time=2020-04-17 12:05:52 (UTC +0000) bamboo_build_time_stamp=2020-04-17T12:04:30.354Z bamboo_build_number=28 project=FWREL-REL6 branch=release/1.5.2
2020-05-19 16:20:27 (UTC +0000) root: MIMO_EVENT ethernet vendor id: 0x221622.
2020-05-19 16:20:28 (UTC +0000) root: MIMO_EVENT Shutdown reason: Reboot by a SW User Process - Ethernet inactivity
2020-05-19 16:20:29 (UTC +0000) root: MIMO_EVENT Startup reason: User Reboot
2020-05-19 16:20:34 (UTC +0000) root: MIMO_EVENT ethernet link up (100/Full)
2020-05-19 16:20:37 (UTC +0000) root: MIMO_EVENT ethernet link emac rx dma stuck
2019-01-01 00:00:07 (UTC +0000) root: MIMO_EVENT no GPS signal for 3 seconds
2020-05-19 16:21:30 (UTC +0000) root: MIMO_EVENT GPS signal recovered
2020-05-19 16:21:42 (UTC +0000) root: MIMO_EVENT Wireless associated
2020-05-19 16:21:58 (UTC +0000) root: MIMO_EVENT ethernet link down

After a few reboot cycles like this things stabilize and the unit remains up with a 100 Mbit/s link active.

The cable has been tested with a Fluke Ethernet tester, no errors are encountered and a 1000 Mbit/s connection is successfully negotiated.

Any ideas on how this situation could be improved?

Why did you end up on CAT7? I have only ever seen Mimosa recommend CAT6.

Have you tested the radio with a shorter cable to make sure the radio isn’t the one at fault?

Also how long is the cable between the PoE injector and the switch/router?

Does the Switch say anything about the link?

Why did you end up on CAT7? I have only ever seen Mimosa recommend CAT6.

Mostly future-proofing reasons, the cable runs in an underground conduit, so re-cabling later would be a hassle. Also, since the same conduit runs multiple network cables (and potentially a power line in the future), wanted to minimize cross-talk and went with outdoor S/FTP CAT7. And last, since 100m is right on the rated limit for this type of cabling, might as well go all in :slight_smile:

Have you tested the radio with a shorter cable to make sure the radio isn’t the one at fault?

Not yet.

Also how long is the cable between the PoE injector and the switch/router?

30 cm.

Does the Switch say anything about the link?

Currently Data to the POE injector is provided by quite a dumb CPE router which essentially reports “link down” or “link restored” states. But you have given me an idea, I will try connecting Data to the POE injector from my laptop so I can use Wireshark to see in more detail what’s going on.

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Just a quick update on the Wireshark front, nothing unusual was spotted, but since I don’t have a professional capture card capable of capturing Layer 1 signals used for auto-negotiation, that does not mean much.

Searching the forums a bit deeper seems to indicate that Ethernet, PoE and auto-negotiation issues have plagued other users as well, like the thread: B5 Rebooting "ethernet link emac rx dma stuck"

Anyone had any luck with RMA with ethernet issues?

Solved the issue.

I should hammer it into my head, that when you are testing the cable, plug and the socket separately, you’re not testing the actual connection, which is a combination of the plug + socket.

Individually both were fine, but when a bit larger when usual (CAT7 compatible) plug was put inside the Mimosa’s weatherproof compression gland and the latter was connected to the unit, some wire failed to connect and only a 100 Mbit/s connection was negotiated. Without the compression gland everything worked fine.

I guess this once again proves that it’s always the simple things, that create the most headache :slight_smile:

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Spoke too soon, I was deceived by the Asus CPE and Mimosa.

They agreed on 1 Gbps, but packet loss was horrendous. Service was only tolerable when the link was forced to 100 Mbps.

However, after doing a deep dive in the forum I found suggestions that an off-the-shelf consumer level switch between the Mimosa POE data port and the CPE port could be of use. Luckily I had a spare TP-Link 10/100/1000 soap box handy.

Lo and behold, the instant the little TP-Link booted up everybody magically settled on Gigabit Ethernet, and there was much rejoicing by me.

Could this be an electrical issue after all and the small switch calms things down, because it is powered by DC instead of AC like the Mimosa POE brick?

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