Rx Overruns on CSS326-24G-2S+RM > 1000 for 1 hour on the uplink port. Traffic is a maximum of 40Mbps on this port. On other ports, traffic is less than 3Mbps and it is all going to the uplink port (all computers work only with the Internet - they do not communicate with each other).
Can the frame buffer size not be enough? What is the frame buffer size? The characteristics are not indicated. Can it be without a buffer?
In the test results, the throughput is 33-43Gbps depending on the size of the packets.
That is 1000 times more than in our mode of operation. Why appear Rx Overruns I do not understand.

the problem is solved - after the firmware update the errors have disappeared

I got the same problem! rx-overruns on the trunk port
i'm running with the latest version (2.7)



Example:
The trunk port is running at 1G full duplex connected to a RB1100Dx4
i'm connected direct to a random port running at 100Mbps
if i ran a btest from another device on a different port running at 100Mbps
on my device... i cant get more than 2Mbps

i tried with flow-control on and off
same thing..

Well here we go again, i got a brand new CRS326-24G-2S+ and the same problem with overruns!!!

The performance just sucks, before the crs i was using a cheap switch with 8 ports and was doing GREAT! idk if im doing something wrong! can someone help me

i'm running the lastest version 6.42.1 RouterOS

Bridge with Hardware-offload ! to several devices

Ether1 work as trunk port to ad RB-1100AHDx4 with a few vlans

Heres the config bellow

/interface bridge
add name=bridge-vlans priority=0x20 vlan-filtering=yes
/interface vlan
add interface=ether1-trunk name=vlan500-mngt vlan-id=500
add interface=bridge-vlans name=vlan2403-mrb-hades vlan-id=2403
add interface=bridge-vlans name=vlan2404 vlan-id=2404
add interface=bridge-vlans name=vlan2405-mrb-aegon vlan-id=2405
add interface=bridge-vlans name=vlan2406 vlan-id=2406
add interface=bridge-vlans name=vlan2407 vlan-id=2407
add interface=bridge-vlans name=vlan2408 vlan-id=2408
add interface=bridge-vlans name=vlan2409 vlan-id=2409
add interface=bridge-vlans name=vlan2411-ptp-loja vlan-id=2411
add interface=bridge-vlans name=vlan2412 vlan-id=2412
add interface=bridge-vlans name=vlan2413-saveiros vlan-id=2413
add interface=bridge-vlans name=vlan2415-mrb-pegasus vlan-id=2415
add interface=bridge-vlans name=vlan2416 vlan-id=2416
add interface=bridge-vlans name=vlan2417-mrb-heimdall vlan-id=2417
add interface=bridge-vlans name=vlan2419-mrb-zeus vlan-id=2419
add interface=bridge-vlans name=vlan2421-mrb-poseidon vlan-id=2421
add interface=bridge-vlans name=vlan2423-mrb-diana vlan-id=2423

/interface bridge port
add bridge=bridge-vlans interface=ether23-mrb-diana pvid=2423
add bridge=bridge-vlans interface=ether19-mrb-zeus pvid=2419
add bridge=bridge-vlans interface=ether17-mrb-heimdall pvid=2417
add bridge=bridge-vlans interface=ether15-mrb-pegasus pvid=2415
add bridge=bridge-vlans interface=ether13-saveiros pvid=2413
add bridge=bridge-vlans interface=ether21-mrb-poseidon pvid=2421
add bridge=bridge-vlans interface=ether3-mrb-hades pvid=2403
add bridge=bridge-vlans interface=ether5-mrb-aegon pvid=2405
add bridge=bridge-vlans interface=ether11-ptp-loja pvid=2411
add bridge=bridge-vlans interface=ether1-trunk
add bridge=bridge-vlans interface=ether2 pvid=2402
add bridge=bridge-vlans interface=ether4 pvid=2404
add bridge=bridge-vlans interface=ether6 pvid=2406
add bridge=bridge-vlans interface=ether7 pvid=2407
add bridge=bridge-vlans interface=ether8 pvid=2408
add bridge=bridge-vlans interface=ether9 pvid=2409
add bridge=bridge-vlans interface=ether10 pvid=2410
add bridge=bridge-vlans interface=ether12 pvid=2412
add bridge=bridge-vlans interface=ether14
add bridge=bridge-vlans interface=ether16 pvid=2416
/interface bridge vlan
add bridge=bridge-vlans tagged=ether1-trunk,bridge-vlans untagged=ether3-mrb-hades vlan-ids=2403
add bridge=bridge-vlans tagged=ether1-trunk,bridge-vlans untagged=ether5-mrb-aegon vlan-ids=2405
add bridge=bridge-vlans tagged=ether1-trunk,bridge-vlans untagged=ether11-ptp-loja vlan-ids=2411
add bridge=bridge-vlans tagged=ether1-trunk,bridge-vlans untagged=ether13-saveiros vlan-ids=2413
add bridge=bridge-vlans tagged=ether1-trunk,bridge-vlans untagged=ether15-mrb-pegasus vlan-ids=2415
add bridge=bridge-vlans tagged=ether1-trunk,bridge-vlans untagged=ether17-mrb-heimdall vlan-ids=2417
add bridge=bridge-vlans tagged=ether1-trunk,bridge-vlans untagged=ether19-mrb-zeus vlan-ids=2419
add bridge=bridge-vlans tagged=ether1-trunk,bridge-vlans untagged=ether21-mrb-poseidon vlan-ids=2421
add bridge=bridge-vlans tagged=ether1-trunk,bridge-vlans untagged=ether23-mrb-diana vlan-ids=2423
add bridge=bridge-vlans tagged=ether1-trunk,bridge-vlans untagged=ether2 vlan-ids=2402
add bridge=bridge-vlans tagged=bridge-vlans,ether1-trunk untagged=ether12 vlan-ids=2412
add bridge=bridge-vlans tagged=ether1-trunk,bridge-vlans untagged=ether10 vlan-ids=2410
add bridge=bridge-vlans tagged=bridge-vlans,ether1-trunk untagged=ether9 vlan-ids=2409
add bridge=bridge-vlans tagged=bridge-vlans,ether1-trunk untagged=ether8 vlan-ids=2408
add bridge=bridge-vlans tagged=bridge-vlans,ether1-trunk untagged=ether7 vlan-ids=2407
add bridge=bridge-vlans tagged=bridge-vlans,ether1-trunk untagged=ether6 vlan-ids=2406
add bridge=bridge-vlans tagged=ether1-trunk,bridge-vlans untagged=ether4 vlan-ids=2404
add bridge=bridge-vlans tagged=ether1-trunk,bridge-vlans untagged=ether16 vlan-ids=2416


Should i just give up on MK Switch?

Did you guys find a solution for the RX Overruns? I'm having exact the same problem. Firmware version 2.7...

Nobody?

I'm having exact the same problem. Firmware version 2.7...

Try mailing support@mikrotik.com instead of posting on the forum. This is a user forum, there's no guarantees MikroTik staff will pick up issues here.

same problem in version 2.8, no mikrotik help at least to know its a bug or i suck configuring it, disabling or enabling IGMP doesnt work, flow control neither, there are times when swich just blocks and i have to restart it in order to function again, i don´t know if it´s related to this Overrrun errors

Hi

I had the same problem.

And I was trying to change firmware, switch ports, settings ... Uplink constantly gets more and more RX Overruns errors (more than 30000 in 12 hours), and a little later another port also get some RX Overruns errors (about 300 for the same time) connected at 100mb.

In the end, it turned out that one of the donwlinks on the remote 100mb switch has a faulty RJ45 connector (not a defective port).

EDIT:
after a few hours RX Overruns errors appears again. e.g. nothing is solved.
Switch is sended back to local dealer (RMA).

Same problem with very simple connection schema and standart switch settings.

Switch CSS326-24G-2S+, firmware ver. 2.8 (built at Fri Jul 13 2018)

Connection scheme: Computer with 1 Gbit/s ethernet adapter - Switch CSS326-24G-2S+ - computer with 100 Mbit/s ethernet adapter.

Trouble description: Rx Overruns counter is raising on the port where 1 Gbit/s computer connected to, performance drops down from 95 Mbit/s to 48 Mbit/s periodically.

Testing conditions:

Switch has standard settings.

Testing program: iperf-3.1.3-win64
Computer 1 Gbit/s: iperf3.exe -s
Computer 100 Mbit/s: iperf3.exe -с 172.30.10.3 -t 15000 -R


Trouble persists during usage in existing network. Test was performed just to locate trouble. We can not use this switch in production

Hi,
I have the same problem with my CSS326-24G-2S+RM ( swos 2.8 ) on router port periodically "Rx Overruns" increase in time.
There is no much traffic on the port, I use this switch in home and router is RB951G-2HND.

Hi, guys.
Below is my previous post.
Now i have 2.6 firmware version on my CSS326-24G-2S+RM and 248 days and 04:53:15 hours uptime. Disabled «Flow control» on uplink port on others it is works.
Upgrading fireware to 2.6 ver and disabling Flow Control on the uplink port helped me to fix this problem in that time.
Not long ago i enabled IGMP Sproofing but i had another problem, not overruns.
.
What about you? Do you have the same problems (with overruns) nowadays?

Rx Overruns on CSS326-24G-2S+RM > 1000 for 1 hour on the uplink port. Traffic is a maximum of 40Mbps on this port. On other ports, traffic is less than 3Mbps and it is all going to the uplink port (all computers work only with the Internet - they do not communicate with each other).
Can the frame buffer size not be enough? What is the frame buffer size? The characteristics are not indicated. Can it be without a buffer?
In the test results, the throughput is 33-43Gbps depending on the size of the packets.
That is 1000 times more than in our mode of operation. Why appear Rx Overruns I do not understand.

Running 2.7 on two CSS326 switches and yes, I do see some RX overruns. Will enable flow control on those ports and see what happens.

Update: Didn't help. Still get RX overruns. Noticed I have these mostly on the ports which are running LACP. Will try without LACP and see if it makes any difference....

Switch has be changed with switch from different vendor, it seems this is the resolution for now ....

i have the same issues with CRS 326 and CRS 328

looks like a CRS 3xx series problem

We are currently testing a new SwOS version for release, this version includes more fixes for performance and packet forwarding related issues which previously has been addressed in RouterOS. If you have a CRS series switch and observe the described problem with packet overruns only when using SwOS and not in RouterOS, then the solution will be in the next SwOS version very soon.

We are currently testing a new SwOS version for release, this version includes more fixes for performance and packet forwarding related issues which previously has been addressed in RouterOS. If you have a CRS series switch and observe the described problem with packet overruns only when using SwOS and not in RouterOS, then the solution will be in the next SwOS version very soon.

That's great news! I'm running RoS on a CRS328 exactly due to FCS errors on the 10Gb interfaces. Fingers crossed, waiting.

Looking forward for a new version! I actually had problems with 2.8 so I reverted to 2.7 which kind of works well enough. But still having the RX overruns and RX FCS errors.

We are currently testing a new SwOS version for release, this version includes more fixes for performance and packet forwarding related issues which previously has been addressed in RouterOS. If you have a CRS series switch and observe the described problem with packet overruns only when using SwOS and not in RouterOS, then the solution will be in the next SwOS version very soon.

Hi!

How soon ?

We are currently testing a new SwOS version for release, this version includes more fixes for performance and packet forwarding related issues which previously has been addressed in RouterOS. If you have a CRS series switch and observe the described problem with packet overruns only when using SwOS and not in RouterOS, then the solution will be in the next SwOS version very soon.

Hi! Any chance to get it for Christmas?

I am also wondering on this. I can see the changelog shows v2.9 when checking for auto updates, but it doesn't seem to be available. RouterOS upgraded SwOS to 2.8p with build date 7/14/18 (yes, there's a p), but this 'p' version doesn't show in the change log or the site. Trying both auto and manual updates fail to install the 2.8 (no 'p') with build date of 10/4/18. They act like they are updating, but come back up with 2.8p again.

Please advise as I'll have to RMA these switches if I can't find a solution soon.

Thank!

Using the SFP instead of an ethernet port for the uplink, solved my overrun (overflow on RouterOS) problem.

Same problem ->
CSS326-24G-2S+RM, SwOS 2.9 with 10G SFP+ upLink to
CRS317-1G-16S+, SwOS 2.7

with disabled flow control :
on CSS326 lots of Rx Overruns
on CRS317 lots of Rx Pauses

with enabled flow control :
lots of Tx/Rx Pauses on both switches
no Tx/Rx Overruns on both switches

Traffic about 1,5 Gbps between two switches - most of it with MTU 9000.

Any ideas - i seem to be lost on this...

I've given up on Mikrotik switches. I have two CSS326 connect through sfp+ fiber (S+85DLC03D in both ends). A lot of RX overruns, some RX FCS Errors and also on many of the other ports, not only the sfp ports. I've now moved almost all equipment to HP switches and only using a two port LAG to the HP switches and the fiberlink. Also enabled flowcontrol on SFP port. Now at least I have no errors but a lot of TX and RX pauses. With the equipment I have I can get ~3,5 Gbps throughput (can't put more load on the link with current setup). The HP switches reports no errors. Running swos 2.9 and have had the same results with earlier versions of swos. My conslusion is that either swos is broken and/or the hardware (CSS326) doesn't have enough capacity (buffers or whatever). So those running the CRS326 with Routeros seems to get it working why I am leaning towards swos problem. I hope the CRS305 and CRS309 are working better since I've been thinking of getting some of those but right now I'm looking at other brands.

Same here!
Lot of tx/rx overruns on 10G port (SFP+ to CRS317) or pauses when flow control is enabled.
I'll wait till next SWoS release and if it is not fixed will throw away and will declare it as another cheap junk.

Same here!
Lot of tx/rx overruns on 10G port (SFP+ to CRS317) or pauses when flow control is enabled.
I'll wait till next SWoS release and if it is not fixed will throw away and will declare it as another cheap junk.

You are welcome to send them to me. I have been very happy with my CRS326 (in SWOS) and two CSS326 switches and would be happy to have a spare I have had no problems with the three, but I'm not trying to connect at 10Gb/s - max of 1Gb/s.

if you thing this is normal - errors tab :
Rx Overruns Tx Pauses SFP tab:

Not my experience. Just looked at one of mine which shows an uptime of 199 days. There is 1 RX Overrun and 0 TX pauses. As I said, nothing faster than 1Gb/s....

Not my experience. Just looked at one of mine which shows an uptime of 199 days. There is 1 RX Overrun and 0 TX pauses. As I said, nothing faster than 1Gb/s....

But with 199 days uptime You are running 2.8, right? I upgraded from 2.8 to 2.9 (CSS326), and saw the increase in Rx Overrruns and Tx Pauses. They are too frequent to my liking, but I don't think they have a real impact on network speed. At least, not for me.

Truth be told, although I use a 10GB trunk, the traffic is light - so maybe it is worse with heavier loads.

=== EDIT ===
10Gb trunk. That typo was killing me!
Better now.
=== /EDIT ==

But with 199 days uptime You are running 2.8, right? I upgraded from 2.8 to 2.9 (CSS326), and saw the increase in Rx Overrruns and Tx Pauses. They are too frequent to my liking, but I don't think they have a real impact on network speed. At least, not for me.

Truth be told, although I use a 10GB trunk, the traffic is light - so maybe it is worse with heavier loads.

Good catch. That one had not been updated. I had forgotten that I had not updated that one yet. I have a bunch of network changes coming up in a few days because of a change in one of my internet connections, so that will be a good time to update that one. A couple routers will also be updated at that time too...

i think its a HOL (Head of LIne) Blocking issue

in mi case it is enough that an download interface (toward clients) negotiate at 100m or 10m is saturated to start to increase dramatically overrun counters on SWos, if running Routeros the count is called overflow in the interface receiving all the traffic from main router

tested with:
CSS 326
CRS 326
CRS 328

That means - we have that problem when traffic passes between interfaces with different speed. Most of people, I think, byes those models to extend 10G networks to old 1G equipment and it's not work...
I receive overruns on 10G eth (up-link) only.

That means - we have that problem when traffic passes between interfaces with different speed. Most of people, I think, byes those models to extend 10G networks to old 1G equipment and it's not work...
I receive overruns on 10G eth (up-link) only.

agree with you, that's the issue, when a down-link port gets saturated the up-link port suffer from overrun/overflow

in my case im only using 1g ports and the issue is present, that imply is not exclusive of 10g uplink vs 1g downlink scenario

i was recommending this switches but from now i am stopping mi customers (mostly isp's) from buying until this issue gets resolved

Same issue on my CSS. Overruns on 10g trunk port and pauses on CRS side running routeros.

Cannot say if it affects the experience a lot, haven't catched any packet loss and the forwarding is not too bad, as I was able to record files to a remote PC at 95Mb/s through an SMB protocol. Haven't tested the actual SFP+ speeds yet as it's only between the network devices. The end users are maximum 1gbit.
Would try to do more speed testing to see if I'm able to push at least 1g simultaneously between multiple PC's.

Отправлено с моего Mi A1 через Tapatalk

Same here... Only overruns, only at one interface 10G

Interface traffic most time is passing 2Gbps+

Linked this CSS326 with CRS317..... with s+da0001

When Flow Control is enabled, we see RX Pauses.
When Flow Control is disabled, we see Rx Overruns

Seems the problem is with CSS326, because, we moved one 10G interface from CSS326 to the CRS317.... and it is running without erros.
No change on modules was made.

Really strange behavior.

I have this same issue 2.10 I am wondering if anyone can say if they have this issue using Mikrotik SFP+ transceiver and any brand of fiber. I am starting to wonder if its a DAC issue. I can see this between my CSS3266-24G-2S+RM and my CRS309-1G-8S+ using a 10m Cisco active Twinax, as well as between my CRS309-1G-8S+ and my ESX host where there is like for like bandwidth and like for like a machine. When pushing 5gbps+ between ESX host that each have 2 10G i interfaces in an active LACP bond between them and the CRS309-1G-8S+, with 3m cisco Twinax.

Even pushing a solid 10gbps and getting this pause incrementing like my utility meter its not a huge impact on latency or bandwidth, but it is a problem if you had more sensitive setup than my home lab.

I have this same issue 2.10 I am wondering if anyone can say if they have this issue using Mikrotik SFP+ transceiver and any brand of fiber. I am starting to wonder if its a DAC issue. I can see this between my CSS3266-24G-2S+RM and my CRS309-1G-8S+ using a 10m Cisco active Twinax, as well as between my CRS309-1G-8S+ and my ESX host where there is like for like bandwidth and like for like a machine. When pushing 5gbps+ between ESX host that each have 2 10G i interfaces in an active LACP bond between them and the CRS309-1G-8S+, with 3m cisco Twinax.

Even pushing a solid 10gbps and getting this pause incrementing like my utility meter its not a huge impact on latency or bandwidth, but it is a problem if you had more sensitive setup than my home lab.

very rare

with 2.10 solved the issue on most scenarios

This is why I am wondering if its the DAC's. On the interface labeled Core94 I can get seeing this type of error as its a 10g link that downstream has to exit 1g link either to a lan device or the fiber internet. However on the esx it doesn't make much sense they each have bonded 10g pairs and I can see in the stats its load balancing pretty well for tx no so well for rx, to generate these errors here I ran a iperf for 3 minutes from esx03 to esx01 and a second iperf from esx03 to esx02. Its very interesting the esx03 got no errors while the other two host got errors, again leading me to ask of three identical network cards, going to the same switch what is different and the only thing is the dac's.

I honestly can say for my current needs its more of a visual issue seeing the errors than an actual issue I notice. But at the same time if swapping out dac's for optical would actually solve the problem then thats what I might have to do.

edit: On closer inspection I would expect it to be TX pause not RX pause on the core94 since its was generated running iperf to my colo so sending from a device behind this switch to an internet location limited to 1g

I can confirm @ploquets behaviour about CCS326-24G-2S+RM having RX pauses with Flow control enabled on the SFP1 with 10GB 3M DAC cable to CRS328-24P-4S SFP1. Both running SWOS 2.10, the RX pauses on the CCS326 are the exact double amount of the TX pauses on the CRS328.

have you tried no flow control at all?

No, indeed haven't disabled flow control I'm already glad I don't see any errors anymore. Haven't had any real issues either since there is almost no traffic on these switches some voip/webbrowsing.

The first thing I'm will to try is change the original 3m mikrotik DAC 10GB cable with another one even optical and than change the trunk port from sfp to a regular 1GB copper port on the switch.

If you look at my screen grab above you can see a list of 3M DAC's that also seem to have this same issue with Flow control enabled. I am really leaning towards trying optics out, if you try optics I would be interested to hear if that fixed it.

@chechito I have never had to disable flow control before, but I have also never used Mikrotik. In my case with 10G host to Switch communication on a single switch with active LACP between the host and the switch, Do you think I should try to disable flow control? I know I need it on my SFP7 link that links my two Mikrotik switches since the devices on the second switch are all 1g.

Thank you all for your time

-Fred

i always use flow control disabled on all installations

i dont understand Why MikroTik do not publish buffer size of any switch on their product line

that info its very important to forecast switch performance

I agree, i'd like to see buffer numbers on all the switching chips to be able to plan.

The Marvell Prestera chipset this switch is based on (98DX3236) is used in a few other platforms and the listed buffer space is 12MB for the 24 port model.

https://eltex-co.com/upload/iblock/9af/ ... 0.1_en.pdf

I have a CRS317-1G-16S+RM as my main switch in my rack, extended via 10GBase-SR and OM3 fiber (Finisar Transducers) to two remote CSS326-24G-2S+RM and one CRS305-1G-4S+.

All the clients attached to the secondary switches are gigabit only.

I have a large number of RX pauses on the SFP+ port on the CRS317 which goes to one of the CSS326 switches. The corresponding SFP+ port on the CSS326 has TX Pauses, (but only about half as many as the CRS317 switch has RX pauses for some reason. I would have thought these would match)

The other CRS326 and the CRS305 are both fine without any pauses.

All of my switches are running SWOS.

Not sure if I am having the same issue as those of you in this thread, if it is a switch hardware issue, a switch software issue, my choice of transducer, or bad fiber that is causing this.

I only used the Finisar transducers because they are what I already had, and they seemed to work.

Signal between the two switches seems perfect with TX dBm on one almost identically matching RX dBm on th eother and vice versa.

Appreciate any thoughts or suggestions.

Try mention above on 317:
Boot RouterOS on it, upgrade it to latest version. upgrade system firmware too. Boot SwOS and upgrade it to latest version. Remove TX/RX flow control on all switches.
Cheers

Try mention above on 317:
Boot RouterOS on it, upgrade it to latest version. upgrade system firmware too. Boot SwOS and upgrade it to latest version. Remove TX/RX flow control on all switches.
Cheers

I'll have to try that when I have some light usage some time. Thnaks for the suggestions.

So are you saying that there is firmware on the router that is not updated when you update SwOS and only updated when you update RouterOS?

I have a CRS317-1G-16S+RM as my main switch in my rack, extended via 10GBase-SR and OM3 fiber (Finisar Transducers) to two remote CSS326-24G-2S+RM and one CRS305-1G-4S+.

All the clients attached to the secondary switches are gigabit only.

I have a large number of RX pauses on the SFP+ port on the CRS317 which goes to one of the CSS326 switches. The corresponding SFP+ port on the CSS326 has TX Pauses, (but only about half as many as the CRS317 switch has RX pauses for some reason. I would have thought these would match)

The other CRS326 and the CRS305 are both fine without any pauses.

Well, I figured out why it was only affecting the ports of one of the two CRS326's was connected to.

Turns out I somehow missed updating it. It was still on SwOS 2.07, or something like that. When I caught it, an dupdated it to 2.12, I now have paus frames on th eports of both the CRS326's

I'm guessing the CRS326 added flow control support somewhere between 2.07 and 2.11.

Fixed on a CSS326-24G-2S+

Downloaded lastest 2.13 and disabled flow control on the port that was giving me errors.

Turns out that port was being used by a PC that was connecting via client to my vivotek camera server (VAST version), the RX overrun errors would start appearing as soon the VAST client initialized and started streaming the cameras.
The switch would eventualy HANG when the user leaves the client running for a day or two, sometimes.

So far no more errors at least.

As of today the RX overflows didnt came back (left the camera client running since yesterday). I did try to replicate the error by reenabling flowcontrol Tx on the same port and still no errors... only a few Tx pauses here and there

Just to clarify, initially I had 2 of these switches with SwOS on them:

- One worked flawlessly for almost 2 years (the one I posted about before)
- The other crapped the bed in less than 6 months. It was hanging for the same reasons, overruns caused from another PC which was ALSO streaming the camera feeds though the VAST client and the user would forgot to turn it off.

I replaced the last one i mentioned (after a year of issues, bought same model for some reason...), and I didn't need to change anything other than upgrading the software to 2.09 at the time, not a single problem after a year and that guy still keeps forgetting to turn off the camera client...

Right now both are upgraded to 2.13.
Both have some connections negotiating at 1G and others at 100Mb, somebody mentioned that could be the cause.
I'll keep testing both and switching the ports around to see what happens.