Does It Matter?

[Elias_Doms]

I have a router connected to a módem by a Cat 5e cable .

If I Connect my pc with a Cat 8 cable to the router, Will the Cat 5e cable limit the Cat 8 cable ? 

[cacoe]

Only if your internet connection is more than a gigabit. (or you have hardware that is capable of > gigabit speeds that you want to use for your local network) 

[Oshino Shinobu]

Not sure why you'd use Cat8. It's designed for very short runs in datacentres, it's not intended for home or office cabling and is only rated to operate properly at up to a maximum of 36m. 

 

Cat6a would be the highest you'd realistically use in a home environment, but unless you have a connection greater than 1Gb/s, there's no point in using anything more than Cat5e

[cacoe]

Just now, Oshino Shinobu said:

Not sure why you'd use Cat8. It's designed for very short runs in datacentres, it's not intended for home or office cabling and is only rated to operate properly at up to a maximum of 36m. 

 

Cat6a would be the highest you'd realistically use in a home environment, but unless you have a connection greater than 1Gb/s, there's no point in using anything more than Cat5e

Op might just have a spare one he... "borrowed" from work  

[TetraSky]

Like others have said, unless your network speed from the ISP is greater than 1Gbps, you'll be fine. Won't change anything for the In/Out speed of your network connection.

As for your local network, expensive Cat8 cables is a bit useless. While they would allow you to reach speeds of up to 40Gbps LOCALLY, the shorter length allowed and price tag associated to these cables may not be worth it compared to a Cat6/6a cable that can reach 10Gbps, which would be more than enough to saturate any SATA SSD and lower end M.2 SSD at over 1GB/s (as compared to Cat5e, which has a maximum theoretical speed of 120MB/s, enough to more or less saturate a normal HDD).
As such, on a home network, Cat5e is "fine" if you don't transfer large files on the regular, but Cat6 is over 8x better than Cat5e, while Cat8 is only 4x better than Cat6... Because there's a point of diminishing return at that point, unless you're transferring 10+GB files between your devices and want it to complete in 3 seconds with Cat8 instead of 10seconds with cat6 (or 90 seconds with Cat5), it might not be worth it (and for video streaming between devices, Cat5e is also more than enough).

 

It also entirely depends on your NIC on your computer. If it's not designed to work with Cat8, you are literally wasting money for nothing. Chances are, it's a Gigabit NIC at most, meaning you can only realistically make use of cables up to Cat5e and you get zero benefits from the Cat8.