Ethernet Cable Switch

[robinbanks]

I can control through python

I don't really know what these ethernet switches do

This is confusing; you can program Python but you don't understand the most basic networking device there is

That's like saying you're a brain surgeon but struggle to work the toaster.. ?

I want to interrupt the Ethernet cable that goes from the recorder to the router.

then your network setup should look like

Internet router
|
Ethernet wire
|
Some cheap switch that is at least as fast as the slowest port it is connected to, plugged into the mains via a timer switch
|
Ethernet wire
|
The network DVR
| | | | | | | |
8 Ethernet wires
| | | | | | | |
8 cameras

The DVR should (might) provide poe to the cameras so they will get their power from the DVR and don't need separate adapters
Or they might need 8 poe injectors, it isn't clear but not really relevant, just get the cameras working however you can

The feed from the DVR to the router is interrupted by cutting the power to the interim switch

If your router or your DVR only has a 100mbit port you don't need to make it a gigabit switch

If your internet upload speed doesn't exceed 100mbit you don't need a gigabit switch

..but switches are so cheap you might as well spend 20 quid on a gigabit one than 15 quid on a 100meg one - just know that it's not vital it be gigabit, just that it be as fast or faster than the slowest thing its linked to