[Solved] Routers (asus n56u & netgear wndr3700) maxed out @ ~250-350mb/s on vanilla OpenWrt. Options to get hw offload working?

Hi. Casual user here.

After an upgrade to ½gigabit, I by accident discovered that my netgear wndr3700 (latest openwrt 18.06) maxed out @ ~250mb/s over lan. I tinkered with a few settings and could get it to ~350. I said 'fåggit', and exchanged it with my old asus n56u (openwrt 14.04) and again saw speeds of only slightly above 250. I said 'fåggit', and slapped my laptop directly on the net, and that gives ~550mb/s, as expected. Tests are done via https://www.dslreports.com/speedtest..

With 2 routers with different versions experiencing same bottleneck, I'll assume that everything OpenWRT-wise are working okay, but that these routers simply are not fast enough. (500 - 650mhz). However, I remember that at least the n56u have hardware for full gigabit on the backplane, so I'll again assume that the driver are proprietary, and not enabled in vanilla Openwrt ?

I hate buying when I can fix. With a little help I can find my way around most problems, but as a casual OpenWrt user, I'm not sure I have the energy to learn how to one-time compile a proprietary blob into the firmware. Assuming my assumption are correct :slight_smile:, what would be a smart solution to getting full speed via my old gear ?


  1. I could just buy a cheap 10$ 1gb/s router in china.
  2. I could revert to asus n56u firmware - for a while.
  3. check out if other firmware have copied/enabled the proprietary blob - Padawan?
  4. Try to squeze as much out of the things with hw/sw tricks. Prolly wouldn't give much.
  5. find out if I can extract and compile openwrt with the blob myself (i did some quick searching without luck).

Additionally on the same subject-ish:

  1. One thing are a massive up/down-loads from a test, but wouldn't a slow router like above still be able to handle smaller bursts at full speed from 1 user ? a small buffer or something ? ..and if, how do one test for such 'burst-speeds' capabilities ?

  2. Both Openwrt 14 and 18 contains newer kernels. Does vanilla OpenWrt prioritise hw/cpu for network traffic, or does it share with installed services ? (in other words, how much does a hard working (ie. compiling) Openwrt slow down routing speed ?)

Thanks. (and special thx to OpenWrt devs+support)

upgrade you wndr3700 to latest snapshot and enable flow-offload

there are also these custom builds with SFE module and some overclock capability that will surely get you to 500mbps

1 Like

Hi Maurer.

That was som great links that I would never have found, thanks, and 'flow-offload' tech was new for me also.

However, the "Enable' part was a bitch :slight_smile: Instructions for earlier builds said to add a forward rule with iptables, and it worked - sort off - but finally I found it somewhere.

The BETA overclocked firmware didn't have a toggle in Luci/firewall, and the first firmware didn't enable Luci, but both had ssh.

I first tried the BETA overclocked (vanilla) and that gave perhaps 5-10% extra speed. Flow-offloading doesn't seem to enable use of HW off-loading, but sw offloading took it to 500+ immediately - on both firmwares.

I'll mark as solved. Thanks a lot..

For those wanting a try at this:
Download Maurer's first link, upgrade.
Log in with ssh (perhaps delete old entry in ~/.ssh/known_hosts)
Add option flow_offloading '1' to the /etc/config/firewall file under the config defaults section."
vi /etc/config/firewall
press 'insert', arrows + edit correct place, press :x
(you survived vi)
/etc/init.d/firewall restart

Perhaps install webinterface?: opkg update; opkg install uhttpd luci

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