Long cable speed drop help needed

RouterOS General
1

Hi,

I hope someone can help me with the issue I’m having… I’ve spent so much time trying to debug this and I still can’t understand what the problem is.

My network scheme is as follows:

[Modem] <=> [Switch] ... 50m cable ... [Station].



  • [Modem] = MikroTik Chateau LTE 12.
  • [Switch] = MikroTik Switch RB260GS.
  • [Station] = any network device on the other end of the long cable. I tried a few laptops, routers, adapters etc.

The cable is long and old and goes to another house and the station connects to the switch @100mbps even though both of them are capable of 1gbps. But that’s not the problem.

The problem is:

  • Speedtest.net on the station shows 12-13mbps only.
  • Mikrotik => Tools => Bandwidth test [Modem] <=> [station] shows 95mbps! (???)

The problem must the the long cable, right? Most probably yes, but just to be sure, I decided to drop out the switch and connect the cable directly to the LTE modem:

[Modem] <=> ... 50m cable ... [Station]

.
Works fine! The speed is ~100mbps.

Okkkk, so the switch works fine without the long cable, and the long cable works fine without the switch, but they don’t work fine together. Bad luck, let’s try another switch… I brought a few other switches I found in my junk box. Using those old switches, I get 25-30mbps, but still far from the speed of the direct connection.

Next I decided to use something else instead of the long cable. I bought a 100mbps linovision coax adapter and installed that in place of the old long cable. The adapter is rated 100mbps up to 1km distance, more than enough for my needs. My new scheme is as follows:

[Modem] <=> [Switch] <=> [Coax] <=> [Station]

Which gives me (surprise!) a speed test of 13mbps on the station…
And it also gives me a 95mbps if I drop out the switch!

Exactly the same results as I had with the 50m cable.

Honestly, I don’t understand why this is happening. Why is the switch connection to the station so much slower than direct connection to LTE modem?

Any help or ideas would be very much appreciated.

2

sounds like the ethernet port of your LTE modem was set to 100Mbps and full duplex mode, not auto negotiation mode. one peer manual fix and the other peer auto negotiation, will cause the auto peer port up as 100/half, that will lost packets when network traffic goes heavy.
but some time one peer fix to 100/full, don’t make any trouble, the other peer can turns up as 100/full. only the other peer is not a switch or a router.

3

The ethernet port of the LTE modem is certainly not fixed: plugging any 1gbps capable device using a proper cable always shows 1gbps connection.

4

IMO presuming cable is not the issue is premature. At 50 meters old Category 3 cables are problematic as link speeds rise. See https://en.wikipedia.org/wiki/Category_3_cable
Try reading the fine print along the length of cable sheath please. If cable is Category 3 then consider fixing the link speed over that cable to 10 Mbps.

5



Maybe it is not clear from my original post, so I will explain. To rule out the long cable problem, I purchased a coax adapter and installed in on a separate coax cable. With the coax setup, I use a perfectly good coax cable instead of the old long ethernet cable. Both of those setups give me slow speed when using the MikroTik switch. Also, both of these setups give me 100mbps speed when connected directly to the LTE modem.

6

Some Mikrotik hardware has issues when running ports at 100mbps. If you have any 1gbps devices on the switch try removing them or force all ports to 100mbps.

7

This sounds like a logical explanation. I’ll give it a try.