ASUS RT-AC66U B1 no longer hitting Gigabit on wired

Jacksonyoung · January 23

Recently switched back to using two of these routers. Using them in an AIMesh setup, but this post is concerning the wired, ethernet speeds. All speed tests have been coming back at around 200ish Mbps down and up. I have AT&T Fiber gigabit internet and ethernet straight from the modem is getting me about 930ish Mbps down and up. Wired speeds were fine in my past router setup (Netgear Orbi). Troubleshooting attempted so far:

- Disabled QoS

- Disabled AiProtection

- Disabled Guest Networks and bandwidth limiters

- Updated firmware (currently on 3.0.0.4.386_51668

- Changed out ethernet cables

- Ensured all cables are, at least, Cat 5e or better

- Rebooted both modem and router(s)

- DHCP query frequency is set to Aggressive (by default)

- NAT Acceleration set to Auto

- Jumbo Frame set to Off

Falcon1986 · January 24

18 hours ago, Jacksonyoung said:

Using them in an AIMesh setup, but this post is concerning the wired, ethernet speeds

How are these 2 units linked? LAN to LAN or LAN to WAN? Also, is the secondary unit also in the "router" operational mode?

18 hours ago, Jacksonyoung said:

All speed tests have been coming back at around 200ish Mbps down and up.

Is there anywhere in the router's interface that allows you to toggle on/off NAT hardware acceleration? Anything related to Level 1 CTF or Level 2 CTF + Flow Accelerator? You might need the latter activated on gigabit connections, although I don't believe the AC66U can route at over 850Mbps WAN-to-LAN or LAN-to-LAN in real world scenarios.

Jacksonyoung · January 24

2 hours ago, Falcon1986 said:

How are these 2 units linked? LAN to LAN or LAN to WAN? Also, is the secondary unit also in the "router" operational mode?

Is there anywhere in the router's interface that allows you to toggle on/off NAT hardware acceleration? Anything related to Level 1 CTF or Level 2 CTF + Flow Accelerator? You might need the latter activated on gigabit connections, although I don't believe the AC66U can route at over 850Mbps WAN-to-LAN or LAN-to-LAN in real world scenarios.

Units are linked LAN to LAN.

NAT Acceleration was set to Auto, which also mentions CTF being enabled.

As an update, rebooting my modem fixed it before bed, but I wake up with everything (both wired and wireless) maxxed out at 100 Mbps.

Falcon1986 · January 24

2 minutes ago, Jacksonyoung said:

NAT Acceleration was set to Auto, which also mentions CTF being enabled.

Can you set it to CTF+FA?

Sorry if I might have missed it, but are you using wireless or wired backhaul for AiMesh?

Jacksonyoung · January 24

1 minute ago, Falcon1986 said:

Can you set it to CTF+FA?

Sorry if I might have missed it, but are you using wireless or wired backhaul for AiMesh?

Using wired backhaul and it is showing "great" connection quality, 1Gbps.

And my only options for Nat Acceleration are "Auto" or "Disable"

Falcon1986 · January 24

43 minutes ago, Jacksonyoung said:

Using wired backhaul and it is showing "great" connection quality, 1Gbps.

And my only options for Nat Acceleration are "Auto" or "Disable"

Test with it disabled to see if that changes anything.

This might be a problem further upstream, i.e. between the ISP device and your first AC66U B1. Check the integrity of the ethernet cable, ensuring it is at least Cat5e or better; no exposed twisted pairs, no sharp bends, etc.