B5c and MikroTik Ethernet Port Flapping

I’ve been having a problem with ethernet port flapping on numerous B5c and B5 radios.

I’m using MikroTik routers at all of these sites. We’ve used shielded Cat6 at all sites and equipment is properly grounded with shielded RJ45 connectors properly terminated.

At some locations, we’ve had very little trouble with this. At other locations, it’s been much worse.

One B5c at one site has been especially bad. So I’m using it as a ‘test site’. At first, the ethernet port connection on this particular radio/router was flapping up and down many times during a day. One day, I could even watch the link light on the MikroTik router going off and on as the ethernet port dropped and came back up.

At this site, on this B5c/MikroTik system, I’ve replaced the POE injector feeding the B5c with a another POE injector from Tycon… I immediately saw an improvement. The flapping has now been dropping a few times a day. But I can’t tolerate hardly anything like this on this system.

I’ve also changed out the MikroTik router, from a CRS326 to an RB1100 (which has dual internal power supplies). I haven’t really seen much of a change in how often the port flaps occur, after this change.

I’ve also tried different configuration settings in the B5c and in both MikroTik routers. None of these have completely stopped the flapping.

I have not tried putting another switch between the B5c POEs and the MikroTik router(s). I’ve read where some have done this and it appeared to fix their problem with port flapping.

Has anyone been able to come up with a real ‘fix’ for this problem and if so, what did you do?

Or should I just stop trying to use MikroTik routers/switches? What brands/models of routers/switches has anyone else been using that doesn’t have this problem with Mimosa radios?

John Rayfield, Jr.

This problem was started at the beginnnig and never resolved.You can’t do anything just change to another device or using optical cable.Everey mimosa devices has this problem with ethernet, but the newer may a littlebit less times than the older ones.B5,B5C,B11,C5C,C5,B24,C5X approximetely in this order.We have some hundred Mimosa Devices but we will change all to back UBNT or higher quality radios like Siklu.Support always told the same stupids, check ethernet cable, grounding ,etc.Our first B5 we never used because this problem.We just waited for resolving for a year, and after Mimosa support said you need to change the devices but already no have warranty. :).I like mimosa from 6. years , i had the first one on Hungary, but it was a very big mistake in my life.I spent lot of money and time for nothing. This is a very big disappointing for me.

Hi John- Same old problem and never a fix! They said they would ship me 4 newer power supplies(grey ones) but never did.

Had to go back to UBNT as Mimosa will not correct there useless ethernet ports!


I don’t think it’s an issue with Mikrotik Routers/Switches specifically. Have lot’s of links both with Mimosa equipment and Other equipment and don’t see the issue.

Is there anything else on the tower? FM radio could be killing you. Other noise making stuff?

Since making the original post here, we’ve done some more testing.

We had a Polyphaser Lightning Protection unit in the Cat6 feed to the B5c. These are high spec (and high priced) lightning protection devices. But, we took it out of the line yesterday afternoon. The B5c and the MikroTik were both set to Auto:1000. About 5 hours later (about 7:00 pm local), I saw the ethernet connection drop and then come back up 3 seconds later. So I ‘locked’ the ethernet ports on both devices to 1000 and so far (as of 1:08 pm local), the ethernet port connection has been 100% solid.

Also, on another B5c at that same site (going into the same MikroTik router), I was seeing quite a bit of port flapping. That B5c is also routed through a Polyphaser Lightning Protector and is also running on the Mimosa POE (gray unit). I left the B5c connected through the lightning protector but I set the ethernet ports on both devices to Auto:100. That ethernet connection has been solid since doing this at about 11:30 am yesterday.

I’m beginning to suspect that auto negotiation at 1000 Mbps, between a B5c and a MikroTik router, is very ‘picky’ and that everything has to be ‘perfect’ for it to work correctly and for the ethernet connection to never drop. Mimosa makes reference to not using additional lightning protection with a B5c (other than what’s in the POE power supplies) and suggest that this might add some extra capacitance to the connection between the router and the B5c. I suspect that extra capacitance in this ‘circuit’ could change the timing of data somewhat, between the router and the B5c, causing the problems with the connection. Setting Auto Negotiation, but using 100 Mbps, would be much less critical with respect to ‘timing’ in the ‘circuit’, so that would explain what I’ve seen so far. Finally, locking the devices to 1000 Mbps, but still reducing extra capacitance in the circuit (removing the lightning protector), would also take the auto negotiation completely out of the picture, so again, ‘timing’ might not be as critical in this ‘circuit’.

I never commented on the grounding at this site. This is a cell site and grounding is very good, outside and inside the building.

I would really like to visit with an engineer at Mimosa (not just telephone tech) to discuss this, to see if I’m ‘on track’ with my testing and the results, so far.

John Rayfield, Jr.

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We have had to install Netgear GS105 switches between some of our Mimosa B11s, B5Cs, and our Mikrotik equipment. It is a quick fix and you can see if the port on the Mimosa has failed or not. If the Mimosa flaps with the GS105 and your cable is good then you have another Mimosa for the junk heap. I would put one inline just as a test.

Thanks Harold. I have a couple of GS105E switches here. I want to set up a way to test this in the shop. I can easily try these switches, then.

So far, after setting the B5c and the MikroTik router back to Auto:100, I haven’t seen any drops at all. It appears that if everything is done ‘right’ (shielded Cat6, connectors put on properly, proper grounding and a good quality POE power supply), then everything will run just fine at Auto:100, but will not work 100% of the time at Auto:1000 or Fixed:1000. I want to figure out why. One thing that I’m not sure of, is which side is dropping first, the B5c or the MikroTik.

John Rayfield, Jr.

We tried all of the “solutions” claimed by Mimosa and others. None of the Mimosa quackery worked. The other solutions offered by real users somewhat worked. What really worked for us (besides going to other manufacturers) was to put a power box pro right next to the B5c’s (we ran fiber to the PBPs) and to run fiber directly to the B11s. No more flapping. We still buy the B11’s knowing we will run fiber, but none of the other Mimosa stuff. It’s too bad, the radio side of the B5c’s is awesome. Ethernet Port Flapping has been a longtime issue with Mimosa.

Dave, what brand of routers/switches have you tried with the Mimosa? I gather that you had ethernet port flapping with other brands, besides MikroTik?

John Rayfield, Jr.