This link of freebsdblog.org suggests a configuration option for FreeBSD that tells the system to drop all packages arriving from the network to a closed port and thus somewhat securing your system and also saving some upload bandwidth as well as cpu time. These are the shell commands to run:

sysctl net.inet.tcp.blackhole=2
sysctl net.inet.udp.blackhole=1

and this you should also insert to the /etc/sysctl.conf file so the settings survive a server reboot:


That's cool so far, but. My Fedora Linux box keeps saying

error: "net.inet.tcp.blackhole" is an unknown key

The quoted parameter names are not listed under /proc/sys, and not returned by sysctl -a.

I found no reference to this problem online. Am I missing something? Do these parameter names differ under Fedora? Do I need some additional package to have this functionality?

Any help is greatly appreciated.

  • Removed freebsd tag – SaveTheRbtz Oct 28 '09 at 17:48

You do realise that Fedora isn't FreeBSD, don't you? To do something similar to this in a Linux distribution, just set the policy on your firewall to be DROP.

  • Yup I do realize. I just thought the same solution could as well exist in both cases. Anyway, thanks very much for the solution! – Mark Szente Oct 28 '09 at 16:54

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