D6400 limited to 20Mbps in download on a Ethernet 100Mbps Connection

[MikDima73]

Hello, 

  I purchased a D6400 router and I am using it on a 100Mbps Internet connection, connected via the Ethernet port. 

The wired thing is that the download speed is limited to 20Mbps, while the upload speed reach 100Mbps with no problem.

The things I tried already are:

• Check that the WAN is configured for Ethernet connection
• Changed the ethernet cable
• Disabled the QoS feature
• Deleted all the QoS rules
• Checking the speed of the Internet connection, and it works at 100Mbps download / 100Mbps upload
• Resetting the router and starting the wizard from scratch
• Updating the firmwar e to the latest version available (V1.0.0.86)

but anyway I cannot download more than 20Mbps. 

It seems to be a bug in the firmware, maybe it is cutting the traffic for a standard ADSL2 connection, but I am connected via Ethernet... 

Anyone can confirm this problem?

Thanks,

MikDima

[MikDima73 · Accepted solution]

Hello, 

    I found the solution. There was a duplex mismatch between the switch and the router. 

On the switch a "show int fa0/29" was showing "full duplex", also in the port configuration there was:

• speed 100
• duplex full

But in the D6400, in the /RST_statistics.htm page, was shown Half-duplex.

In this case I just set the port on the switch with "auto-negotiation" (no speed 100, no duplex full) and now the /RST_statistics.htm page shows 100M/Full. 

Now the speed is 100Mbit both for downloads and uploads.

I post this solution just to share with the world, that might be helpful to other people... 

Thanks to all!!

Michele

[MikDima73]

EDIT: I also set the MTU to 1400 but it did not solve the problem. 

[DexterJB]

Hi @MikDima73,

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Dexter

[MikDima73 · Accepted solution]

Hello, 

    I found the solution. There was a duplex mismatch between the switch and the router. 

On the switch a "show int fa0/29" was showing "full duplex", also in the port configuration there was:

• speed 100
• duplex full

But in the D6400, in the /RST_statistics.htm page, was shown Half-duplex.

In this case I just set the port on the switch with "auto-negotiation" (no speed 100, no duplex full) and now the /RST_statistics.htm page shows 100M/Full. 

Now the speed is 100Mbit both for downloads and uploads.

I post this solution just to share with the world, that might be helpful to other people... 

Thanks to all!!

Michele