C5x Ethernet Port Flapping

Are any of you having this issue with your C5x’s? We’ve been experiencing the issue for sometime now and have tried everything. We’ve changed firmware (currently 2.5.3 and 2.8.1) and tested cables. It seems to be happening with most of our clients. We have most of our CPE’s connected to Cambium R190w’s and Mikrotik Hap Lites. It seems to be happening globally and just can’t seem to figure it out. Any help would be appreciated! Thank you
2021-06-22 08_32_56-C5x

After further investigation it’s also happening on EVERY AP we have it seems. Very frustrating

So you are having issues with your A5 hardware as well? Or are you using your C5x radios in PTP mode?

The timing looks a lot like a router rebooting. (The grouping of the link flaps and the timing between each flap)

Is it the AP side, the client side, or both?

The devices you said that the C5x units are plugged into only have 100 Mbps ports. Have you tried adjusting the Network Interfaces section on the Management tab of the C5x to turn off Autonegotiation and set it manually to 100/Full or, if that doesn’t help, uncheck the 1000BaseT-Full option so that it doesn’t even try to negotiate that?

Under Miscellaneous on the Management tab, is Rapid Port Shutdown enabled? If so, does turning that off help?

1 Like

We’ve also had this problem with C5x and B5c radios, and to some extent (but not as much) A5c radios. We’re very careful that we have proper grounding and we’re using Cat6 on the A5x, B5c and A5c radios. We’re using Cat5e on the C5x radios, but it’s a good quality cable and the runs are often very short, maybe 30 feet or even less. Proper grounding and good quality cable (and connectors put on properly) can definitely make a difference with this problem, but these things do not appear to be a ‘total fix’.

We’re using MikroTik routers of various models, including the RB951G, RB2011, RB4011 and the CRS125 units.

I did find that if I set the MikroTiks to Auto, but only for 100 Mbps or 1 Gbps, and the Mimosa radios are set to auto and all speeds, then this does seem to help reduce the problem, but it doesn’t always stop the port flapping completely. Locking the C5x and the B5c radios to 100 Mbps does appear to stop the port flapping.

So for customers at, or under, 100 Mbps we’re locking the C5x at 100 Mbps. We aren’t offering any service at over 100 Mbps yet, so this hasn’t been a problem, yet. But it seems to be a compatibility problem between the ethernet chip (or circuit) used in the Mimosa equipment and that used in the MikroTik (and apparently other brands, too).

Interestingly, this isn’t a problem with just Mimosa. I found a document on Cisco’s website that explains how a feature in some of their equipment works, that is designed to reduce port flapping. Apparently, this is a problem throughout the router/switch industry.

One local engineer with whom I spoke, thinks that it’s a timing problem, which would explain why things work at a slower speed (100 Mbps) but doesn’t work at a higher speed (1000 Mbps). I haven’t found anyone else who has gone any further in determining exactly why this is happening and how to fix it.

I would very much like to visit with engineers at Mimosa about this, if anyone knows how I can reach them.

John Rayfield, Jr.
Rayfield Communications

1 Like