1. W. Odom, CCNA Routing and Switching 200–120 Official Cert Guide Library Book, ISBN: 978–1587143878, May 2013
2. P. Browning, F. Tafa, D. Gheorghe, D. Barinic, Cisco CCNA in 60 Days, ISBN: 0956989292, March 2014
3. G. Heap, L. Maynes, CCNA Piratical Studies Book (Cisco Press, April 2002)
4. Information IT Online Library.: http://www.informit.com/library/content.aspx?b=CCNA_Practical_Studies&seqNum=12
5. Inter NIC (InterNIC is a registered service mark of the US Department of Commerce. It is licensed to the Internet Corporation for Assigned Names and Numbers, which operates this website)—Public Information Regarding Internet Domain Name Registration Services, Inter NIC, Online: https://lookup.icann.org/