IP addresses are categorized as either public or private. According to the IANA (Internet Assigned Numbers Authority), the following are reserved for private use:
* 10.0.0.0 to 10.255.255.255 (Class A Private)
* 172.16.0.0 to 172.31.255.255 (Class B Private)
* 192.168.0.0 to 192.168.255.255 (Class C Private)
Any IP outside of these ranges is considered public and routable on the global internet.
Evaluation of each option:
* A. 172.168.254.2 # This is in the 172.16.0.0 - 172.31.255.255 range # Private
* B. 172.28.73.21 # Also falls in the same private 172.16.0.0/12 range # Private
* C. 11.63.72.21 # Outside all private ranges # Public#
* D. 10.110.50.37 # In the 10.0.0.0/8 range # Private
* E. 192.168.0.1 # In the 192.168.0.0/16 private range # Private
Extract from Rene Meneses MTCNA Study Guide:
"Private IP ranges include 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16. These are non-routable over the public internet." Extract from Terry Combs Notes:
"Only IPs outside of the above ranges are considered public and routable. Watch out for 172.X.X.X - not all are public; only 172.0.0.0-172.15.255.255 and 172.32.0.0+ are public." MikroTik Wiki - IP Addressing Reference:
"Private addresses are not globally routable. They are used inside local networks and must be NATed for internet access."