Cannot get higher than 100 MBPS over ethernet using ASUS RT N66U

A

asperity

Limp Gawd
Joined
Feb 19, 2014
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143
I am a complete router/modem/networking noob and I need some help here.

I have a cable modem: ARRIS/Motorola Surfboard SB6183
And a router: ASUS RT-N66U
My motherboard: ASUS Maximus VI Formula (Onboard Lan: Intel I217-V 10/100/1000 MBPS)

Now I recently just got an upgrade to my internet from 100/5 DL/UL to 300/20 DL/UL from TWC. If I connect my computer directly to the modem, I get the max rated speeds on different speedtests which is 300/20 DL/UL. Now if I connect the modem to the router's WAN port and my computer to the router's LAN port and run the speed test I can only seem to get a maximum of 100/20 DL/UL. I'm trying to find out the reason why I cannot get the full rated speed when using the router. Any thoughts?
 
Because speedtests are inaccurate?
You might want to check if the Asus enables some smart "QoS" by default.
//Danne
 
Well they tend to be consistent with if I have my computer connected to the router or directly to the modem, the speeds anyway. Lower speeds while on the router on multiple tests, while the higher speeds directly connected to the modem on multiple tests. QoS is off by default.
 
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Try a different PC with a Gigabit Ethernet port, and try connecting to a different Ethernet port on the router. If you are still not getting the faster speeds via the router, try a different router. It could be the router is the cause, even though it has Gigabit WAN/LAN ports.
 
My bet is that the problem is with the WAN port auto-negotiating the wrong speed. Is there any way for you to hard code the link speed to gigabit on the router?
 
Have you tried different cables between the router and the modem? It's possible that it's not perfect and the router falls back to 100mbits with it, while the computer can use it as gigabit. Also what type of cable is it? There has to be a writing on it that will say: CAT5, CAT5e, CAT5 Enhanced, or CAT6
 
Verify the link between the PC and router is running at gigabit. If it is, then make sure the link between modem and router is running at gigabit as well.
 
I know that the connection between my router and pc is gigabit, but I am not sure if the connection between my router and modem is gigabit. Both are using Cat5e cables.
 
Sounds like an auto negotiation issue between cable modem and router wan port which is usually a configuration, cable, firmware or interoperability issue.

1. Go into your router's management interface and make sure the wan port is configured for auto negotiation and gigabit is enabled.
2. Call your ISP and make sure the cable modem is configured the same.
3. Try a new CAT6 cable.
4. Update firmware to latest firmware.
5. If the those don't help try putting a gigabit switch (preferably non-Broadcom like Qualcomm/Atheros or Marvell since the RT-N66U is Broadcom based) between cable modem and router.
 
I think I have located the problem, it seems that the WAN connection from the modem to the router is at 100 MBPS. It shows an orange led on the modem when it is connected to the router. I have tried several cat5e cables and they all produce the orange LED.
 
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