RT-AC68U getting less than 50% bandwidth only 1 wired connection

[Sensisnow]

After recently purchasing my RT-AC68U it's been working great, aside from one very frustrating issue.

I have a 50Mb fiber connection to my home, which includes Fioptics cable. If I connect my gaming PC directly to the cable modem with a wired connection I consistently get ~28Mb/s after cable overhead is accounted for, which is perfectly acceptable.

If I connect Modem -> RT-AC68U -> Netgear Switch -> (different)PC I get the same results at ~28Mb/s.

However, if I connect my gaming PC to the RT-AC68U my speeds are never more than ~12Mb/s, which is less than half the available bandwidth. YouTube videos are constantly buffering as well, which shouldn't be an issue with even a 12Mb/s connection.

I'm running the latest Merlin build with factory default settings.
Wireless connection is working with great speeds.
Another wired connection running through a switch is getting 28Mb/s.
Wired connection directly from cable modem to gaming PC gets 28Mb/s.
Wired connection to gaming PC running through RT-AC68U using same ethernet cable is limited to 12Mb/s.

I spent hours scouring forums trying to find a solution last night, but nothing seems to be working and I need help!

Does anyone know what might be the cause of this?

 

[Sensisnow]

Update.

Tried more troubleshooting last night to no avail. I got the same results as in my previous post, which were around 12Mb/s using the wired connection to the router.

I finally got too frustrated to deal with it anymore so I plugged in a wireless-N dongle that I had laying around and instantly and consistently got 40Mb/s. The higher bandwidth compared to my original post was due to fewer cable boxes being used at the time.

I can deal with the slightly increased latency using a wireless connection, but I would still prefer to keep things wired if anyone has any insight as to what might be causing this issue.

 

[krislerok]

Do you have the "Enable Smart QoS" enabled? Did you define any QoS settings?

 

[TonyH]

Hi,
Also what is NIC on the gaming PC? Checked advanced setting on that card?

 

[Sensisnow]

Do you have the "Enable Smart QoS" enabled? Did you define any QoS settings?

No, I don't have QoS enabled, nor are any settings defined.

 

[krislerok]

TonyH makes a good point, what about the NIC settings? Please check to see if they're set to half-duplex, etc. Please check for Auto-Sensing or force it to the highest setting.

 

[Sensisnow]

Hi,
Also what is NIC on the gaming PC? Checked advanced setting on that card?

The NIC I'm using is the controller integrated into my Gigabyte GA-X79-UD3 motherboard. It works flawlessly when connected directly to my cable modem and also had no issues when connected to my previous Netgear router.

I haven't checked the advanced settings on it, but nothing has been changed since upgrading my router. Is there anything specific that I should be looking for?

Thanks for the reply!

 

[Sensisnow]

TonyH makes a good point, what about the NIC settings? Please check to see if they're set to half-duplex, etc. Please check for Auto-Sensing or force it to the highest setting.

Thanks for the suggestion, I'll check that out when I get home this evening.