What command would you use to disable a second network interface in Linux?

To disable a second network interface in Linux, the appropriate command is one that effectively turns off that specific interface. In this case, using 'ifdown eth1' is the correct choice because this command is specifically designed to bring down network interfaces that were previously brought up using the 'ifup' command.

When the 'ifdown' command is executed with the interface name (in this instance, 'eth1'), it takes the necessary steps to deactivate that network interface, ensuring that it no longer sends or receives any network traffic. This is a crucial operation for managing network connections in a Linux environment, particularly when you want to temporarily disable an interface for maintenance or troubleshooting.

Other commands provided serve different purposes. For example, 'ifup eth1' would attempt to activate the interface instead of disabling it. 'ifconfig eth1 down' does successfully disable the interface as well but is considered a more deprecated method in favor of the newer 'ip' commands. Lastly, 'shutdown eth1' is not a valid command in this context, as 'shutdown' is typically used to power down the entire system rather than managing individual network interfaces.