Hi All,
I’ve recently upgraded my home Internet connection to 100Mbit/2.5Mbit. I run a cable modem in bridge mode, and use a MikroTik 750g for routing.
My problem is slow speed (20Mbit) through the 750g. If I remove the 750g from the equation I get the full 118Mbit!
I thought the 750g would be able to easily handle 100Mbit routing. Have I configured something wrong?
Any troubleshooting help will be appreciated.
Regards,
Lomax
I have a 750gl (which is 400Mhz as opposed to your 680Mhz faster CPU) and it gets me 52Mb from my Cable Modem.
So, 20Mb shouldnt be the limit.
Make sure you have the latest firmware 5.14 (as of this post).
Also make sure you arent using bridges. You can slave other ports off a single one to use the faster switch chip.
ie if your LAN is ether1, and you want ports 2-4 to be also “LAN”, then make 2-4 slave to 1.
If you do have a bridge, you need to delete it, remove the interfaces from it, then reboot the router, then do the slave adjustments, otherwise you will get a “ether2 is a member of a bridge already” error.
Even with bridging it should be able to handle way much than 100Mbps (mine bridges at ~400 Mbps according to Iperf).
Thanks for your input guys. The switch ports are slaved off a single port.
Mikrotik support said to check the CPU clock. It was indeed set to 100Mhz instead of 680Mhz (go figure - an upgrade must have done this?). I set it to what it should be (680Mhz), rebooted, confirmed setting, and ran my tests again. Still no joy but certainly less load on the CPU.
I’ve put my Cisco back in for now and am running at full speed again.
Any further troubleshooting suggestions?
I would suggest posting an /export compact so we can see your config ?
Config export attached.
ConfigExport20120303.rsc (24.3 KB)
That looks like a full export.
Under RoS 5.14 you can do “export compact” which will just print your changes from factory default. 
Which modem do you have? My routerboard won’t get any ip address from Motorola Surfboard SB6120. My D-Link and Cisco routers have no problem getting ip address from Motorola modem. MK support refused to fix it and blame it on Motorola, so my only choice is to replace the modem, so I’m curious which modem you have.
What different CPU clock settings have you tried?
I had really bad DL performance with my 750g (firmware 5.15), round 3-4Mbit/s (my LAN, cable modem and internet connection should be able to handle >100Mbit/s).
After I’ve read this thread I decided to check my CPU clock and guess what, it was set to 100MHz (how could that be possible?) !
I set it to 680MHz and my DL performance was really improved, now round 40-60Mbit/s.
When I tried 600MHz I got even better DL perfomance, round 80Mbit/s, that was a little bit unexpected, how come 600MHz will perform better than 680MHz!?
I then saw that it was possible to set it to 800MHz (overclocking in some way I guess) and with 800MHz I get full speed in DL (> 100 Mbit/s) !
Regards
Hans
It depends what are you doing with your connection. Few months ago I was running 150 clients on 750g: 100+100mb from 2 isps. Router was doing simple queues, dhcp, lots of firewall, policy routing, graphing, had quite often poll from the dude and api client. With conntrack on, depending on session count, it was able to show numbers of upto all the 200mbps..
I can confirm that overclocking indeed improves performance: on times when cpu was 100%, overclock reduced it to some 92% or so. Sometimes it simply widened the bottleneck.
So the bottom line is that rb750g along with rb750 is one of the most successful routers MT ever made. Mine got rebooted only for upgrades. It lasted for half a year once, so this definitely counts. I suggest to blame the router in the last place.