Cisco documentation: http://www.cisco.com/univercd/home/home.htm
Cisco conventions: http://www.cisco.com/warp/public/459/techtip_conventions.html
IETF: http://www.ietf.org/
National Vulnerability Database: http://www.nvd.nist.gov
NSA Switch Guide: http://www.nsa.gov/snac/os/switch-guide-version1_01.pdf
NSA Router Guide: http://www.nsa.gov/snac/routers/C4-040R-02.pdf
Assigned port numbers, essential for reading access lists: http://www.iana.org/assignments/port-numbers
Valid but unassigned IP blocks: http://www.iana.org/assignments/ipv4-address-space
Original ISO OSI Standard: http://www.standards.iso.org/ittf/PubliclyAvailableStandards/s020269_ISO_IEC_7498-1_1994(E).zip