Everything else is set to defaults in both Basic Settings and WL-Advanced.
What's happening is, within 30 minutes of the ddwrt router booting, I get essentially identical bandwidth (up and down) benchmarks with all wired clients regardless of the OS they're using (Linux and OS X). This benchmarking is essentially identical as well, when those wired clients are switched to using wireless to directly connect to the wireless network (not through ddwrt). So this is very good.
That's roughly 22Mbps down.
After 30 minutes (a rough estimate, I don't have a huge sample size at this point) this performance tanks to at best 1.5Mbps, and is often half that amount. If I switch computers to wireless they benchmark at 22Mbps; back to wired with the ddwrt router, back to 1.5Mbps; reboot ddwrt and for ~30min, wired benchmarks come in again around 22Mbps.
My only hint so far is, if I go to the sys-info page (Info.htm), under the Wireless section is the AP the router is connected to. After boot, TX RATE and RX RATE are both 117M and I get ~22Mbps bandwidth tests. When this drops to 1.5 (or less) Mbps, the TX RATE is 130M but RX RATE is 1M. But it fluctuates from 1M to 130M, being at 1M about the same amount of time as 130M.
The first three of the AP Mac address is B4:C7:99 which translates as Zebra Technologies Inc. There are 7 wireless APs in this network, and all clients: ddwrt, laptop, NUC, Android phone, always connect to the same AP MAC address.
Two more are on channel 11. Two on 1. And one on 6. The one with the highest RSSI (lowest negative value) is the one listed above.
I'm not sure how to get more information on what might be happening after 30minutes of activity, I guess I'll turn on syslogd, reboot, and see if that reveals anything.
I've done a hard reset, and flashed to DD-WRT v3.0-r29739 vpn-special (05/19/16), using dd-wrt.v24_vpn_special_wrt600n.bin.
The RX RATE going to 1M then back to 117 or 130M is a goose chase. That happens regardless of the fast.com and speedtest.net outcome.
Right now, 46 minutes after rebooting from the firmware flashing, I'm still getting 26Mbps from fast.com. I'll see how it goes over the next day and report back.
The problem persists as described, even after reset and flashing. So I'm out of ideas how to trouble shoot this.
Consistently it's the WRT600N in client mode. Whenever I use another client: laptop, NUC, phone, I get 20+Mbps where the WRT600N in client mode barely gets 1.5Mbps, until rebooted.
Whereas if I use the WRT600N in AP mode, just as a test, I can still push/pull ~80Mbps. So my best guess is that somehow the client mode just breaks, doesn't like the AP hardware it's connected to, something that I don't understand.
