HOW TO : Route traffic to loopback interface in Linux

Back in 2009 (last decade!! :) ), I wrote a blog post on how you can trick windows to route traffic destined to a particular IP address to a black-hole. In it, I mentioned the command to route traffic to /dev/null in Linux was

<code>route ADD IP_ADDRESS_OF_MAIL_SERVER MASK 255.255.255.255 127.0.0.1</code> 

I ran into a need to try it today and looks like the trick doesn’t work :). So here is the right command if you want to route traffic to the loopback (or blackhole) destined to a particular IP address

sudo route add -host IP_ADDRESS_OF_HOST/NETWORK_MASK lo 

For example if I want to black-hole traffic destined to 74.205.216.2, I would do the following

 sudo route add -host 74.205.216.2/32 lo 

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