I'm experiencing slow upload speeds when connecting my computer to the 2.5g port operating at 2.5g. If I remove the 2.5g full advertisement from the ether1 interface (forcing the computer to negotiate to 1g full) I do not experience the slow upload speed.
My Setup:
I have my internet on a 1g port (ether8) and I have the 2.5g port connected to my computer which has a built in Intel I225-V NIC which supports 2.5g full.
Internet -> (ether8 1g) RB5009 (ether1 2.5g) -> Computer with Intel I225-V supporting 2.5g
In my use case I have a 1g symmetric internet connection but I have my computer attached to the 2.5g port as a server so that it can access the internet and serve my 1g home network at the same time without losing bandwidth. All of my devices are connected to the RB5009, I do not have any other routers or switches in my setup (small home setup).
I have noticed that if I allow ether1 to advertise 2.5g, my computer will auto-negotiate to 2.5g (as expected) but my upload speed drops compared to that of a direct connection. If I remove the 2.5g full advertisement from ether1 the computer will auto-negotiate to 1g (as expected) and my upload will increase to expected
Here is my data:
Direct connection (no RB5009): 950/950 Mbps which is expected
2.5g Full: 950/600 Mbps which is 300 Mbps lower on upload
1g Full: 950/950 Mbps which is the same as a direct connection
I'm using Ookla for my speed test and these results are very consistent as I have swapped back and forth between these configurations several times. Whatever is happening appears to be systematic rather than random. There is something about the port operating at 2.5g and routing to my 1g WAN port that is causing a slow down only on upload (faster 2.5g interface sending).
I tried enabling RX and TX flow control on both the 2.5g port and the 1g WAN port but I got the same results.
I'm running RouterOS 7.1.2. I also tested 7.0.5 and 7.1.1 and all of the versions show the same slow down (I upgraded from 7.0.5 to see if a newer version would fix this issue which is why I tested older versions).
I have done a bunch of searching on this problem but most people are connecting their 2.5g port for WAN whereas I'm using it on my computer side and my WAN side is a 1g port (ether1). I don't have any 10g devices and I'm not using the SFP+ port.