Slow PPPoE with RT-AC68U and gigabit fiber

[NoSync]

Hi,
I got a gigabit fiber connection (the ISP's ONT is connected directly to my RT-AC68U, which is using PPPoE with a specific VLAN tag) and in the recent firmware releases my WAN speed degraded dramatically.

Up until 380.68 I was getting around 900 mbit/sec from my connection, whereas from 380.69 on (including the currently running 384.4 beta3) I can't get more than 450 mbit with AiProtection disabled (380 when enabled, while Adaptive QoS doesn't really make a difference).

HW acceleration is obviously enabled (only CTF, since my RT-AC68U is one of the earliest units and it doesn't support FA), and disabling it nets me below 300 mbit speed, which is expected with this router.

I tried resetting the ONT, factory restoring the router, cloning the ISP router's MAC address, and every other possibly conceivable thing. Nothing useful in the connection logs - apart from the speed everything works perfectly, very decent bufferbloat, etc. The ISP's router (a locked down, custom Huawei unit) gets full speed.

I can't spot anything relevant in the changelogs of 380.69 or NG, so I can only assume it's something coming from Asus's GPL code. Any ideas?

Thanks.

 

[Vexira]

Have you attempted a factory reset after the firmware upgrade ?

 

[NoSync]

Yep, not with 380.69 but with 384.4 I started from scratch.

 

[bandit8623]

Hi,
I got a gigabit fiber connection (the ISP's ONT is connected directly to my RT-AC68U, which is using PPPoE with a specific VLAN tag) and in the recent firmware releases my WAN speed degraded dramatically.

Up until 380.68 I was getting around 900 mbit/sec from my connection, whereas from 380.69 on (including the currently running 384.4 beta3) I can't get more than 450 mbit with AiProtection disabled (380 when enabled, while Adaptive QoS doesn't really make a difference).

HW acceleration is obviously enabled (only CTF, since my RT-AC68U is one of the earliest units and it doesn't support FA), and disabling it nets me below 300 mbit speed, which is expected with this router.

I tried resetting the ONT, factory restoring the router, cloning the ISP router's MAC address, and every other possibly conceivable thing. Nothing useful in the connection logs - apart from the speed everything works perfectly, very decent bufferbloat, etc. The ISP's router (a locked down, custom Huawei unit) gets full speed.

I can't spot anything relevant in the changelogs of 380.69 or NG, so I can only assume it's something coming from Asus's GPL code. Any ideas?

Thanks.

So if you go back to 380.69 you get back to 940? just checking to make sure its not a ctl issue with bandwidth exhaust.

 

[NoSync]

So if you go back to 380.69 you get back to 940? just checking to make sure its not a ctl issue with bandwidth exhaust.

Not on CenturyLink but on Vodafone Italy, the connection is a full gbit no matter the time of the day, but reverting back to 380.68 and 380.69 for a test won’t hurt anyway - I’ll try as soon as I can and report back. Thanks.

 

[Ashish Gupta]

I have the EXACT same problem. Get 980+ if I connect the ISP modem directly to my laptop. If I use the ac68u in PPPOE mode I get ~600mbps with h/w acceleration ( AI protect / qos etc off )

 

[bandit8623]

I have the EXACT same problem. Get 980+ if I connect the ISP modem directly to my laptop. If I use the ac68u in PPPOE mode I get ~600mbps with h/w acceleration ( AI protect / qos etc off )

so going back to 380.69 fixes the speed issue ?

 

[doczenith1]

There are known issues with fast PPPoE connections and some of the recent firmware versions. I suggest doing a search you will find some answers.

 

[bandit8623]

There are known issues with fast PPPoE connections and some of the recent firmware versions. I suggest d0ing a search you will find some answers.

The reason im curious about this is my friend has latest merlin with 68u on gig and doesn't see more than 550 600. And thats using dhcp. Connected directly to modem he sees 940. Haven't tried the older firmware release yet

 

[Ashish Gupta]

I used to get 900+ on some old version ( don't know which ) and then it broke. I haven't flashed any old version back as I am fine with 600+

 

[NoSync]

There are known issues with fast PPPoE connections and some of the recent firmware versions. I suggest doing a search you will find some answers.

Yep, I did, but nothing conclusive really. What I could gather is:

- PPPoE NAT acceleration at a certain point was broken, possibly only for those users who require VLAN tagging
- In 384.3 it was fixed for most models (I assume not for the RT-AC68U)
- A user solved his problems by installing a managed switch (which would do the VLAN tagging) between the ONT and the router.

So I guess there’s not much to do for the time being, and this leads me to believe the problem lies with using PPPoE and VLAN tagging together.

The weird thing is that the performance with HW acceleration enabled is not the same as with it being explicitly disabled, so I guess this bug breaks acceleration somewhat but not quite completely.

 

[NoSync]

Update: I tried (almost) all firmwares back to 380.67, and no changes - PPPoE still slow. I'm bummed.

I also tested again with my ISP's router, and sure enough I get my >940 mbit via cable, so I ordered a managed switch in order to do VLAN tagging there and disable it on the RT-AC68U. I should get it tomorrow for some more tests.

If that also doesn't work I have only two options left:

1) Get something such as an EdgeRouter to do the PPPoE part and keep the AC68U as an access point, but by doing so I'd lose QoS as the ERs do not have offloading for it and their CPU is slow, hence I wouldn't be able to get over 200 mbit or so

2) Upgrade to an 86U

This said, since PPPoE speed used to be just fine with my 68U, under the same firmware releases I tried tonight, at this point I'm starting to suspect it could be something with the hardware. Is that possible?

 

[bandit8623]

Update: I tried (almost) all firmwares back to 380.67, and no changes - PPPoE still slow. I'm bummed.

I also tested again with my ISP's router, and sure enough I get my >940 mbit via cable, so I ordered a managed switch in order to do VLAN tagging there and disable it on the RT-AC68U. I should get it tomorrow for some more tests.

If that also doesn't work I have only two options left:

1) Get something such as an EdgeRouter to do the PPPoE part and keep the AC68U as an access point, but by doing so I'd lose QoS as the ERs do not have offloading for it and their CPU is slow, hence I wouldn't be able to get over 200 mbit or so

2) Upgrade to an 86U

This said, since PPPoE speed used to be just fine with my 68U, under the same firmware releases I tried tonight, at this point I'm starting to suspect it could be something with the hardware. Is that possible?

On non ppoe (dhcp) seeing max of 500 on newest firmware. On 380.69 seeing 900. Same settings for both. So definitely an issue with newest releases.

 

[NoSync]

Ok, I got my managed switch and tested with VLAN tagging there as opposed as on the router - no changes whatsoever, so I guess VLAN tagging is not the culprit here.

On non ppoe (dhcp) seeing max of 500 on newest firmware. On 380.69 seeing 900. Same settings for both. So definitely an issue with newest releases.

This is interesting, as it would seem to completely exclude PPPoE and any related configurations. It might be limited to some units, though, as I assume way more people have their WAN configured with DHCP but I don't think I've seen any complaints to date.

Could you please try asking your friend to switch his 68U to AP mode? If he gets full speed with that setup then I'd assume the issue lies in NAT acceleration not working correctly; if not, it's probably some hardware issue (switching).

 

[bandit8623]

sorry it took so long to respond. i dont have access to my buddies router anymore. and my 68u at home here i only have 300mbps service so i cant test.

 

[NoSync]

sorry it took so long to respond. i dont have access to my buddies router anymore. and my 68u at home here i only have 300mbps service so i cant test.

No worries. I got an RT-AC86U and I’m back to full speed.

 

[bandit8623]

No worries. I got an RT-AC86U and I’m back to full speed.

what kind of cpu usage do you see with the 86u when fully on gig through wan? glad your back to full speed

 

[NoSync]

what kind of cpu usage do you see with the 86u when fully on gig through wan? glad your back to full speed

I don’t have a wired client at hand at the moment, but if I launch a Speedtest on two wireless clients at the same time, the combined usage of the two cores peaks at about 50% (out of 200%, obviously).

 

[bandit8623]

I don’t have a wired client at hand at the moment, but if I launch a Speedtest on two wireless clients at the same time, the combined usage of the two cores peaks at about 50% (out of 200%, obviously).

thanks!

 

[Smokie]

I know this an old thread but wondering if anyone resolved the issue without replacing the router? I just switched providers and connected my RT-AC5300 to the ONT, configured my vlan tag as instructed but can't get more than 150m on my 1000m line.

I was running the latest merlin firmware and tried to jump back one or two but the issue is still there.

QOS is not enabled and putting the IPS router online gives me the full 1000.

I did notice if I connect my laptop directly to the ONT I get the same speed as when the asus router is connected, although my network adapter is showing 1G connection.