CBK40 6Mbps Upload on Xfinity Gigabit

[isaiah1112]

I recently aquired a new Orbi CBK40 Router/Modem combo to replace my CM1100 modem and a Nighthawk Router.  I have Xfinity gigabit service and on a normal day I see 400+Mbps download and 40Mbps upload speeds.  However, after installing the Orbi my upload speed seems to be limited to 6Mbps upload even though my download speeds were now consistently in the 650Mbps+ range.

I called Xfinity, tested running different configurations of cables; not going through a splitter, etc.  Nothing worked.  Called Netgear support only to have them attempting to tweak wifi settings on the Orbi.  After some explaining this was NOT a wifi issue but upload speeds on the WAN side of the Orbi I was told to set the MTU to 1472 or try a Cat7 cable (insert facepalm here). 

After doing factory resets on the Orbi, ensuring the firmware is up-to-date, and scouring the internet (I did find another post that seems to be almost the exact same issue: https://community.netgear.com/t5/Orbi/rbr40-firmware-update-slowed-down-internet-speed/m-p/1775915#M...) I've decided to go back to my previous setup.  The second I plugged back in my CM1100 I immediately was back to getting 40Mbps upload. 

Not sure if anyone has any ideas around why this might be.  The fact that the only device that changed was the CM1100 and the Orbi (which I've heard is a CM700 modem) I'm not sure what else to try.  I've been doing some research into the fact that the CM1100 is DOCSIS 3.1 where the CM700 is only DOCSIS 3.0.   However, everything I've read seems to point to the CM700 even being able to support 40Mbps upload speeds.

I have other screenshots/files if anyone is interested of the QAM frequencies/channels for each modem.

[FURRYe38]

What Firmware is currently loaded?

Has a factory reset and setup from scratch been performed since last update?

Be sure there are not coax cable line splitters in between the CBR40 and ISP service box. 

MTU should be set for 1500 and not anything lower. 

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@isaiah1112 wrote:

I recently aquired a new Orbi CBK40 Router/Modem combo to replace my CM1100 modem and a Nighthawk Router.  I have Xfinity gigabit service and on a normal day I see 400+Mbps download and 40Mbps upload speeds.  However, after installing the Orbi my upload speed seems to be limited to 6Mbps upload even though my download speeds were now consistently in the 650Mbps+ range.

I called Xfinity, tested running different configurations of cables; not going through a splitter, etc.  Nothing worked.  Called Netgear support only to have them attempting to tweak wifi settings on the Orbi.  After some explaining this was NOT a wifi issue but upload speeds on the WAN side of the Orbi I was told to set the MTU to 1472 or try a Cat7 cable (insert facepalm here). 

After doing factory resets on the Orbi, ensuring the firmware is up-to-date, and scouring the internet (I did find another post that seems to be almost the exact same issue: https://community.netgear.com/t5/Orbi/rbr40-firmware-update-slowed-down-internet-speed/m-p/1775915#M...) I've decided to go back to my previous setup.  The second I plugged back in my CM1100 I immediately was back to getting 40Mbps upload. 

Not sure if anyone has any ideas around why this might be.  The fact that the only device that changed was the CM1100 and the Orbi (which I've heard is a CM700 modem) I'm not sure what else to try.  I've been doing some research into the fact that the CM1100 is DOCSIS 3.1 where the CM700 is only DOCSIS 3.0.   However, everything I've read seems to point to the CM700 even being able to support 40Mbps upload speeds.

I have other screenshots/files if anyone is interested of the QAM frequencies/channels for each modem.

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[isaiah1112]

Pretty sure it was 2.3.5.12 and yes, factory reset was done after the update. I do see there is a 2.3.5.30 and 2.3.5.34 that seem to be available. Maybe I’ll have to try those although nothing in the release notes hints that anything was fixed related to this issue.

[FURRYe38]

Please re-confirm those FW versions. I don't see those listed here:

https://www.netgear.com/support/product/CBK40.aspx#download

Ensure the MTU is set for 1500.

[isaiah1112]

My bad. The 2.3.5.30/34/36 are for the satellite.

The router/modem is running 2.3.5.12

[FURRYe38]

So what happens if you factory reset the CBR40, setup from scratch, don't enable speedtest, access controls or traffic meter or change the MTU value on the CBR40. Just wire connect a PC and speed test with Ooklas installable speed test app. 

[isaiah1112]

I believe that is what I did upon the initial factory reset.  However, I will attempt to run another test this weekend of exactly that to see what happens and will post an update as soon as I have the resutls.

[FURRYe38]

Let us know. 

This was my speeds about a year ago when I had my CBK40 online:

https://community.netgear.com/t5/Orbi-with-Built-in-Cable-Modem/CBR40-Speed-Test-Results/m-p/1663025...

I would work with the ISP service. Ask for a tech to come check it all out. If it turns out everything is good on there side, then we'll need to contact NG support. Possible FW issue or you may have a bad unit.