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Reduced WAN Speed on RT-N66U with Shibby 116

Discussion in 'Tomato Firmware' started by blacklotus83, Apr 12, 2014.

  1. blacklotus83

    blacklotus83 Network Newbie Member

    Hi there

    I'm using tomato for many years now and came from WRT-54GL to 3500L and since two years I'm happy with my RT-N66U, thanks shibby for the great work here!

    Since beginning of the month my provider upgraded my Internet connection to 250 Mb down and 15 Mb up. After some testing I found out that with tomato I reach "only" around 210 Mb, when I connect directly to the modem I constantly have 250. I then went back on original Asus firmware and also merlins version and with both i get the full 250.
    But the original firmware lacks many tomato features I use so, I went back on tomato.

    After a clean installation of tomato 116, 64k, AiO (SDK 5) and after NVRAM cleaning I reach again max down-speeds of around 210. I deactivated everything (USB, FTP, QoS etc.) but speeds do not get better. Is this a known bug or do you have any ideas?

    Anyone else who could test that?

    Best regards
    Last edited: Apr 12, 2014
  2. rs232

    rs232 Network Guru Member

    MBps I guess is not correct, either Mb or MB, in general network speeds are always expressed in bit per second (bps) so I guess you're talking about 250Mb and 15Mb? (NOTE: capital B always refers to Bytes).
    Going back to to your question you might want to look into bmc_nat Ref: http://www.linksysinfo.org/index.php?threads/two-quetions-on-bcm_nat.69234/

    Personally I'm unclear on how tomato is affecting (if!) the hardware capabilities.

  3. Marcel Tunks

    Marcel Tunks Networkin' Nut Member

    Absence of the fastnat and CTF modules is responsible for the lower max throughput, in exchange for the traffic monitoring and other capabilities of Tomato. Victek's speedtest builds will get higher throughput with some other Tomato functions removed. If you need all of Tomato's features then you can consider accepting the lower throughput or moving to a supported ARM based router when those builds are a bit more refined.
  4. blacklotus83

    blacklotus83 Network Newbie Member


    Thanks for your replies. Of course I meant Megabits, thanks for the hint.

    Okay I read some things about about fastnat. I tested the "modprobe bcm_nat" option in the init script and after a restart I have the full speed of 255 Mb behind the router. As I do not use QoS, BW Limiter or Access Restrictions I'll give it a try and look how the router runs in general with that option.

    However, shouldn't the n66u be enough powerful to handle the connections without losing bandwith... Maybe I'll give the new Linksys WRT AC1900 a try in a few months.

    Best regards
  5. Marcel Tunks

    Marcel Tunks Networkin' Nut Member

    Glad you've got it working.

    The CPUs in consumer routers aren't powerful enough to sustain high throughput without taking shortcuts, such as bypassing parts of netfilter (CTF). The same drop in throughput occurs if you activate QoS on stock firmware because fastnat and CTF can't be used. If you develop the need for some of those features in the future then you can consider an ARM-based router, but right now they are more expensive than finding an old laptop or desktop, adding a second ethernet card, and running a firewall distro. I'd wait for a price drop.

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