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mattk92
join:2015-12-22
Seattle, WA

mattk92

Member

half speed downloads with CenturyLink Fiber, ASUS RT-AC87U+ Merlin

I finally ditched my Technicolor C2000T, and upgraded my RT-AC87U to the Merlin firmware and followed all the instructions from here:

»CenturyLink 1 Gigabit speed cut in half using my own Asus Router
and
»CenturyLink 1GiG Fiber with ASUS RT-AC3200 Speeds and Settings

After setting the proper PPPoE creds, the internet is fine, but download speeds are still capped at 50%. I've turned off the router multiple times and rebooted after 5 mins, but still I get the same result.

Do I need to do a factory reset to see the speed increase?
gapmn
join:2013-11-10
Saint Paul, MN

gapmn

Member

yes, do a factory reset after the software upgrade to Merlin.
ChefJoe
join:2015-06-08
Seattle, WA

ChefJoe to mattk92

Member

to mattk92
Are you at 50% of 40 mbit level service (so, 20 mbit) or are you paying for gigabit and your speed tests keep coming back at ~500 mbit ?
avx
join:2015-12-12
Osseo, MN
(Software) pfSense
Netgear RAX120
Netgear RAXE500

4 edits

avx to mattk92

Member

to mattk92
Might have something to do with CTF (Cut Through Forwarding is Broadcom's proprietary acceleration feature) being disabled, which reduces throughput on these Broadcom based units. I believe PPPOE, QoS, and traffic metering all disable CTF, which causes reduced speeds. I believe its the same even for the newer AC5300 routers using Broadcom chipsets. Qualcomm based routers don't suffer from this issue.

I think RMerlin the custom firmware creator himself has a better explanation on SmallNetbuilder forums:
»www.snbforums.com/thread ··· n.18144/

If you think I made a mistake anywhere please feel free to correct me.
mattk92
join:2015-12-22
Seattle, WA

1 recommendation

mattk92 to ChefJoe

Member

to ChefJoe
I'm paying for gigabit, and I'm getting around 400 mbit download, 950 mbit upload
mattk92

1 recommendation

mattk92 to avx

Member

to avx
CTF is enabled. I'm going to try a factory reset, I bet that resolves it.
avx
join:2015-12-12
Osseo, MN
(Software) pfSense
Netgear RAX120
Netgear RAXE500

4 edits

avx

Member

Maybe you have CTF but with Flow Acceleration off or incompatible settings are overriding the CTF user option? Have you tried wired to just your C2000T as a test?
Forgive me if any of the questions seem pointless, I don't actually own that device.

Mid way through the link below it mentions some combinations of CTF/FA:
»routerguide.net/nat-acce ··· -or-off/
mattk92
join:2015-12-22
Seattle, WA

1 recommendation

mattk92

Member

After doing a factory reset of my Asus, I'm still only getting 50% download speed. CTF is set to auto, QoS is off, Port Forwarding is off, traffic monitoring is off, and turned off STP (as instructed here: »www.snbforums.com/thread ··· t-196387).

I have also tried wiring directly to the C2000T, and it worked great. No issues -- full bandwidth up and down.

I'm beginning to believe I can't turn on Flow Acceleration because I'm using PPPoE (»www.snbforums.com/thread ··· t-203098)

Is that accurate?
avx
join:2015-12-12
Osseo, MN
(Software) pfSense
Netgear RAX120
Netgear RAXE500

4 edits

1 recommendation

avx

Member

I believe so, maybe let the C2000T do the PPPOE and put the Asus router in the C2000T's DMZ to bypass its inbuilt firewall.

I know my old Netgear R8000 and current R7000 also have similar issues according to SNB forums due to the same/similar Broadcom chipset, but my internet is only 40/2 so it does not affect me. Since you have gigabit internet it is a big dip in throughput though.
mattk92
join:2015-12-22
Seattle, WA

1 recommendation

mattk92

Member

Interesting. This guy describes how to turn on FA, but for the life of me (regardless if I'm using PPPoE or not) I can NOT turn it on. Any other ideas?

»www.rickygao.com/tuning- ··· ormance/
avx
join:2015-12-12
Osseo, MN

1 edit

avx

Member

redacted
mattk92
join:2015-12-22
Seattle, WA

1 recommendation

mattk92

Member

Wow. OK, after much debugging, I've discovered the only way to get FA working is to turn off PPPoE and use Automatic IP. Thus, I've fixed my original problem (which was bandwidth being halved), but I still need to route traffic via my C2000T. It's not possible to remove it on CenturyLink and still keep gigabit download speeds.
avx
join:2015-12-12
Osseo, MN
(Software) pfSense
Netgear RAX120
Netgear RAXE500

1 recommendation

avx

Member

Your best bet at avoiding the C2000T is to use a Qualcomm SoC based router like the Linksys EA8500 or Netgear R7500v2 but its probably not worth spending on a new router just to avoid the C2000T though, as you have a pretty good one already. Probably best to wait till next year when 8x8 AC routers start showing up.