Can a LAN adapter cause a whole home network to crash?

I was searching for a LAN adapter on Amazon.

One of the reviews stated that this LAN adapter caused a crash of their home network. The router would restart a lot and the laptop wouldn't have an internet connection. Removing the adapter solved the problem.

In case you want to read the review, here it is (on German): https://www.amazon.de/gp/customer-reviews/R3P59KQU3K8MB2/

I am just wondering, how or if that could even be possible? Doesn't the LAN adapter just "convert" the signal and not mess with IPs? Shouldn't the router just not deliver the signal to a faulty LAN adapter instead of restarting itself?

Maybe the buyer had a bad router?

Solution 1:

Yes, it's possible for an Ethernet device to sabotage the entire network. At work, a core switch died and started flooding the network with invalid Ethernet frames at ~700 MBits/s. This caused all PCs on the network to overload the CPU so much even moving the mouse no longer properly worked.

Of course, non-PC devices could be affected by problems like that as well.

Solution 2:

Absolutely yes.

There are many ways an Ethernet device can kill a network, especially a network with low consumer-grade equipment.

It can spam out malformed packets, swamping the router.
It can have a MAC address that matches an existing device on the network. Yes, this should not be possible. Also YES, it can and does happen.)
It can have a null MAC address, and your network has a router or device that cannot work with this.
I have even encountered an Ethernet device that output 220V on a PoE line, toasting everything downstream!

If your network is managed by a real device, say a decent Cisco router that is correctly configured, it will simply detect and isolate the malfunctioning/misbehaving device. But at household level? Nope.