Modem works, but not recognized by routers

[alanmushnick]

HI

I was trying to ditch my xfinity rented modem. Set up the Netgear CM700 easily with one short call to give them the MAC and Serial numbers. It was on the Xfinity list of approved hardware. 

Instantly was able to use my HP Windows 10 laptop with the ethernet cable. Fast browsing. no issues. 

Then when I plugged the ethernet cable into my Airport Extreme, no signal was recognized. 

Same results when I used ethernet cable to an Eero Pro to try to set that up. 

Yadda yadda, after multiple restarts/resets of all devices I was forced to call Xfinity and reinstall their rented modem.  Then no problem creating a new wireless network with the Eero Pro. 

Why would the modem's ethernet output work perfectly when hard wired to my HP laptop, yet no signal was recognized when I tried TWO different wireless routers, the Airport Extreme or the Eero Pro.

Any help is appreciated. Trying to avoid the rental fees. 

[FURRYe38]

Did you power OFF the modem and connected router for 1 minute, then back on with the modem first, then the router to see if the router and modem got connected? 

[alanmushnick]

Actually each time I rebooted CM700 I used the Ethernet port first with laptop to assure that it was getting proper signal to rout and browse. Then I would take the Ethernet out of laptop and install on the Eero. And then power up Eero.

I could try your idea But I would have to go thru the process of calling Xfinity again to list the Netgear as the modem on my account. Not sure when I'll be at that house but may try again on more time. 
I wonder why it would matter?
thanks for help

[Joi007]

2 issues here.

#1 if you set up your router with a particular modem and then swap out modems. There is a chance that it will not recognize the new modem because the router had been originally configured with a different modem.  2 fixes.

Fix #1  Step 1. unplug both the modem coaxial cable, ethernet, and power down the CM.

            Step 2. unplug the cable modem from the CM and disconnect power supply.

            Step 3. Plug everything back in and power-up the CM first.

            Step 4. Plug everything back in and power-up the router second

If Fix #1 doesn't work try Fix #2

Reconfigure the router from the very beginning. Reset it and begin the installation of the router process again like you did when it was brand new.  It should pick up your new CM at that point.

BUT before you do any of that I would recommend you switch to the NETGEAR CM600 since the CM700 has the dreaded Intel 6 PUMA chipset.  You're NETGEAR CM700 is on the avoid list linked below.

I recommend the NETGEAR CM600 as they use a Broadcom chipset.  I use the CM600 and can verify it is 100% okay as I have run several tests with PingPlotter Pro and there is not latency issue with it.

https://approvedmodemlist.com/intel-puma-6-modem-list-chipset-defects/ 

Intel Puma 6 Defect Explained
Intel’s Puma 6 chipset included in several cable modems is defective as it allows high spikes in network latency quite often (slow web page loading, for example). These severe network latency spikes interfere with online gaming, streaming video, or simply surfing the web. Network jitter (variable latency) also causes problems.

The Puma 6 modems suffer from both latency and jitter. Some firmware updates have only temporarily fixed the problem and it seems Intel has no real fix for the issue. Consequently, these bad internet connections landed cable modem maker ARRIS in trouble with a pending lawsuit filed in California.

[FURRYe38]

By powering OFF the CM modem and host router for 1 minute and back on will not require you to contact the ISP. The ISP already has the modem associated with your account using it's MAC address. 

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@alanmushnick wrote:

Actually each time I rebooted CM700 I used the Ethernet port first with laptop to assure that it was getting proper signal to rout and browse. Then I would take the Ethernet out of laptop and install on the Eero. And then power up Eero.

I could try your idea But I would have to go thru the process of calling Xfinity again to list the Netgear as the modem on my account. Not sure when I'll be at that house but may try again on more time. 
I wonder why it would matter?
thanks for help

---

[Joi007]

@alanmushnick 

Please contacted the ISP and give them the new MAC address for the NEW Cable Modem (CM).  The NEW CM has to be authorized by the provider and added to your account for it to work.  The OLD CM MAC address will be removed. That is even before my FIX #1 instruction.

[Joi007]

CM's equipped with Intel Puma 6 & 7 chipsets.

Puma 6 spikes - Pingplotter Pro video

[FURRYe38]

Anyone wanting more info on Intel based modems can check out this site as well:

http://www.badmodems.com

CM1000/1100 and 1200 are all broadcom based modems. 

[Joi007]

Thanks for sharing... It appears his Netgear CM700 is listed on that site aswell. Return it for a what Furrye38 recommends.  I'm using the CM600 and that one is safe aswell.

Having internet not working is NO fun.  Hope this helps.