An edge security gateway is configured to drop any outgoing packet to the public Internet if its source IP address belongs to an RFC 1918 private address space. During a security audit of un-translated egress traffic logs, four source IPv4 addresses were recorded. Which source IPv4 address is globally routable on the public Internet and will be permitted through the firewall filter?
- 172.32.10.55Answer
- B172.30.100.1
- C192.168.100.255
- D10.255.254.1
Answer
172.32.10.55 is a public IPv4 address because it falls outside the RFC 1918 Class B private address allocation (172.16.0.0/12).
RFC 1918 allocates three specific ranges for private networks: 10.0.0.0/8 (10.0.0.0 - 10.255.255.255), 172.16.0.0/12 (172.16.0.0 - 172.31.255.255), and 192.168.0.0/16 (192.168.0.0 - 192.168.255.255). The address 172.32.10.55 begins with 172.32, which is higher than the upper boundary of 172.31.255.255, making it a globally routable public address that passes the RFC 1918 egress filter.
Step-by-Step Solution
Key Concept
RFC 1918 Private IPv4 Address Space Boundaries
Estimated Time:1m 0s