It's easy if you know how.
Archive of posts filed under the linux category.
Quick and dirty IPv6 with 6to4
Get IPv6 here and now. Even if your ISP does not support it.
OpenVPN’s built-in packet filter
Control client-to-client connections in bridged mode (and more).
iptables debugging
Using the raw table with the TRACE target
Tun/Tap interface tutorial
How tun/tap works in Linux, with sample code
