Ethernet Port Flapping on MikroTik Routers

RouterOS General
1

I’m having a problem with multiple MikroTik Routers, such as the CRS326 and CCR1036.

I’m using Mimosa wireless equipment connected to these routers/switches. Mimosa radios are locked to 1 Gbps on the ethernet ports and the MikroTik equipment is all set to Auto Negotiate but is set to only use 1 Gbps. I’ve tried locking the MikroTik units to 1 Gbps, but this did not help the problem.

The problem is port flapping, where the ethernet ports will drop and then within a few seconds, come back up.

I’ve seen that this appears to be an ongoing problem with MikroTik routers/switches but I’m hoping that someone has come up with a real ‘fix’ for this. I really like the MikroTik equipment, but I’ve either got to have a real fix for this problem, or I’m going to have to find another brand of routers/switches that don’t have this problem.

John Rayfield, Jr.

2

Mimosa radios are locked to 1 Gbps on the ethernet ports

Undo that! All ports should be set to “auto”, for the link negotiation to work correctly.
When you want 1 Gbps or nothing, set only the “advertise” checkmarks for 1 Gbps, do not lock speeds.

3

So set Auto Negotiate on both Mimosa and MikroTik, but it is ok to set both to only Negotiate at 1 Gbps. Is that what you mean?

I had not tried this combination of settings.

John Rayfield, Jr.

4

Yes you can do that. It will bring almost nothing when compared to an auto setting with all speeds advertised, the only difference is that the link will fail completely instead of negotiate to 100 Mbps e.g. in case of a partial cable failure or out-of-spec cable, but when that is what you want it is OK to set it that way.
Disabling autonegotiate completely and set fixed speed is a recipe for problems, especially at 1 Gbps.

5

I tried setting Mimosa to Auto 1 Gbps and MikroTik at Auto 1 Gbps and had a ‘flap’ fairly soon after that. So this did not fix the problem.

John Rayfield, Jr.

6

I would suggest to leave everything at defaults and see if it switches back to 100 or 10 Mbps or still goes down completely.

7

I’ve already tried defaults. That’s why I’ve tried other settings, because defaults were terrible, with a lot of ‘port flapping’.

John Rayfield, Jr.

8

Which model of Mimosa do you use?

9

See if you can reproduce the issue with a short pre-made cable.
How are you powering the APs? Is there some additional power inserter inbetween?

10

Cabling is good at all sites. Cat6, shielded with connectors put on properly (we’ve seen a lot that aren’t put on properly).

Mimosa radios are powered with POEs from Mimosa.

We do have lightning protection on the Cat6 cables and I’m beginning to wonder about that, at some sites. Last night and this morning, one connection at one site was going up and down like a yo-yo, a lot. That site has different lightning protectors on the Cat6 cables as compared to some of the other sites. I’m going to swap out those lightning protectors with the ones that we usually use and see what happens.

John Rayfield, Jr.

11

For me it usually works fine, except on a single site where there is a RB750Gr3 connected to an outdoor UBNT dish and it has ever changing speed.
That site is a radio/TV broadcast tower where multiple kilowatts of FM, DAB+ and DVB-T2 are transmitted.
I think the problem is related to that (RF interference).
It is a longtime running plan to redo the installation with a small outdoor metal cabinet near the link dish instead of long cable run to the top floor.