Slow Throughput behind Mikrotik

We recently got a new circuit from Spectrum and immediately after install the technician launched a speedtest on Ookla to show speeds. Ookla shows over 200Mbps down from a laptop directly connected to the modem.

We then installed a CRS 112 and ran the test from the laptop from behind the Mikrotik. The speeds are only 27Mbps.

I also tried one of the public bandwidth test servers mentioned here http://forum.mikrotik.com/t/public-mikrotik-bandwidth-test-server-s-now-shutdown-as-of-april-1st-2025/94863/1 and got 40Mbps using udp.

I’ve tried toggling the duplex from 100 Full, 1G Full, 10G. Did a speedtest for each of those configurations and 100 Full is really slow, 1G Full breaks the connection, and 10G is really slow.

There are 7 firewall filter rules, 4 NAT rules, and no queues. I’m having a problem interpreting these results and explaining the discrepancy to users behind this firewall.

Any assistance would be greatly appreciated. Thanks!

Do you have fasttrack rules?

The CRS is a switch, with very little router speed. Take a look at the numbers, on the product page:

https://mikrotik.com/product/CRS112-8G-4S-IN

Down there, at the bottom, You will see that its speed with 25 ip rules is about 95 Mb/s. As a switch, it reaches wirespeed on all ports. As a router… well.

Cool, I didn’t think of that. I implemented as seen here https://wiki.mikrotik.com/wiki/Manual:IP/Fasttrack and the tests look good now.

I am curious about the placement of the fasttrack rule. Since its placed in the forward chain, where is the optimal placement? Should it be above input chain rules?

What are the pro/cons of fasttrack? Not really sure I understand what it does internally. Is there anything I should watching regarding resource consumption? Are there any scenarios when fasttrack would not be a good idea?

Yes if you want to use queues. They don’t work with fasttrack. With gasttrack you use less ressources. Place it after the input rule.

Only benefits for a common usage