Installing scapy with all of it's functionality on Gentoo.

get scapy, as root:

wget http://hg.secdev.org/scapy/raw-file/tip/scapy.py
chmod 750 && cp scapy /usr/local/sbin/
emerge -av gnuplot-py pyx pycrypto ebtables

The dependency biggie is gnuplot (X doc emacs gd ggi pdflib plotutils png
readline svga xemacs)
I used: USE="X gd plotutils png readline"

ebtables I pulled in to get /etc/ethertypes

If you are still on Python 2.3 run:

python-updater

If you skip this step you won't be able to plot.

After that you are done!

Getting Started using scapy:

 - http://www.secdev.org/projects/scapy/#demo
 - http://www.secdev.org/conf/scapy_Aachen.pdf

Scapy home: http://www.secdev.org/projects/scapy/