Why does it say 4x ethernet ports in your description where there is only one

Actually, because Amazon shows the same questions/descriptions for multiple different products. The CM1200 has four ports, the CM1000 has one.

With the cm1200 and xfinity residential cable internet, can you use one wan port to your computer for a direct connection and on wan port to router?

Both the CM1150V and CM1200 have 4 Ethernet ports. That does not mean you don't need a router. These four Ethernet ports support future multi-gig services by using link aggregation and two or more different IP addresses. The CM1100 has two Ethernet ports for the same purpose of future link aggregation. If you want a multi-gig cable modem (2.5 Gbps) without the need for aggregation, you'd like the CM2000 or CM2050V with XFINITY voice support. I know NETGEAR does not do a very good job explaining this to potential buyers and I hope this helps someone. CM1100 - https://amzn.to/3peEGGR

So, up to 2gbit modem with - drumroll please - 1gbit network ports. not 2.5gbit. which engineer was responsible for this fail?

which "engineer"? It was probably "beancounters" in marketing. this CM1200 model has 4 ethernet ports. but only 2 are functional. the first 2 ports can be Link Aggregated, to get downloads up to 2 Gbps. the other 2 ports are mere decoration to trick naive trusting people to buy this model. not to overlook, Netgear only certifies this model to 800 Mbps with Xfinity. that's what it says here in the ad. (and also on Netgear website)

Can I replace my existing cable modem from Spectrum with this, on my own/ without a service call or having to call customer service?

Replacing your modem does not require a service call, but you will need to call Spectrum customer service, as they will need to activate the modem as an authorized device on their network before it will be able to lock down a connection. You will need to provide them with the unique MAC address of the device - specified on the modem's label. Customer service calls can be irritating, but when I did the same a month or so ago, the tech knew what needed to be done and the entire call, once speaking with the tech, lasted about 5 minutes - little hassle...this time.

ASIN	B08GWNZ9VF
Best Sellers Rank	#258 in Computers & Accessories ( See Top 100 in Computers & Accessories ) #3 in Computer Networking Modems
Brand	NETGEAR
Built-In Media	Nighthawk 2.5Gbps Internet Speed Cable Modem (CM2000), One (1) Ethernet cable, Quick install guide, Power adapter
Color	black
Compatible Devices	Router
Connectivity Technology	Ethernet
Customer Reviews	4.2 out of 5 stars 2,941 Reviews
Data Transfer Rate	2.5 Gigabits Per Second
Internet Service Provider	Cox, Spectrum, Xfinity
Internet service provider	Cox, Spectrum, Xfinity
Item Dimensions L x W x H	9.92"L x 4.7"W x 8.7"H
Item Type Name	Cable Modem
Item Weight	1.02 Pounds
Manufacturer	Netgear
Maximum Downstream Data Transfer Rate	2.5 Gigabits Per Second
Maximum Upstream Data Transfer Rate	2.5 Gigabits Per Second
Modem Type	Cable
Number of Ethernet Ports	1
Number of Ports	1
Product Dimensions	9.92"L x 4.7"W x 8.7"H
UPC	606449147452
Unit Count	1.0 Count
Warranty Description	1-year warranty

Nighthawk Multi-Gig Cable Modem (CM2000) - Compatible With All Cable Providers Incl. Xfinity, Spectrum, Cox - For Cable Plans up to 2.5Gbps - DOCSIS 3.1

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