Hi there, I’m trying to optimize my RB751U running v6.40.3 for my new fiber internet connection. It’s connected to the fiber modem that is running in bridge mode. I establish the PPPoE client connection from the Mikrotik. I’m seeing weird things happen with the download speed:
- Speedtest.net always reports very good (for this service) download/upload speeds of 11/6 megabits, no matter what MTU I use and no matter which test server I try.
- When I download 100MB test files from hosting providers that have good networks (like Ramnode, Linode, and DigitalOcean) I get all sorts of fluctuation. For example, I might try Ramnode and get only 40 KB/sec downloads, and then immediately after I try Linode and get 1.2 MB/sec.
- The speeds are highly dependent on the max-MTU that I manually set for the PPPoE connection. In the situation I mentioned before, if I get very slow download speeds from Ramnode but very fast speeds from Linode, I can slightly adjust the MTU and reverse the scenario, making Ramnode very fast at 1.2 MB/sec but Linode only getting 40 KB/sec.
- I’ve tried every sort of MTU value from 1440 all the way up to 1488 (the maximum that this connection supports), and any given value makes some of my test sites download very fast while at the same time degenerating the speed for others, and each time I change it the fast and slow sites change. I can’t find a single value that’s good for all the sites.
When I leave the max-MTU value blank, RouterOS shows that it defaults to an MTU of 1480, and it’s always that same value. This results in good speeds for some sites and very slow downloads from others. Shouldn’t RouterOS automatically calculate the optimal MTU for each connection? Any idea why this is happening?
Thanks a lot.