Quiz — IP Addressing
Test your knowledge of IPv4, subnetting, IPv6, and public vs private IPs
IP Addressing — Knowledge Check
You read 32-bit dotted decimal, worked /24 versus /26, met IPv6 (::1, fe80::, dual stack), and split RFC1918 from the address a website sees after NAT. These ten APPLY scenarios test judgment — not octet trivia. Choose the best defensive or lab move.
APPLY: ip -br addr shows lo 127.0.0.1/8 and wlan0 192.168.1.42/24. A teammate on another continent asks you to "SSH to your IP" using 127.0.0.1. What failed in their mental model?
APPLY: You must decide whether 192.168.1.50 and 192.168.1.70 are on-link neighbors. Both masks are /26. What is the right calculation?
APPLY: A junior pastes a 20-row CIDR table into Slack but cannot say why /24 has 256 addresses. What should they have done instead?
APPLY: True or False: An IPv4 address in a log is equivalent to a password: it uniquely authenticates a human and must be stored only in a vault.
APPLY: ip -6 addr shows ::1 and fe80::abcd on eth0, plus a global 2001:db8::10. IPv4 sshd is firewalled. sshd also listens on [::]:22. Best SOC move?
APPLY: Which statement about IPv6 compression is the one you would trust in a ticket?
APPLY: Home ip addr shows 192.168.0.12/24. A trusted "what is my IP" page shows 198.51.100.7. CGNAT might even sit in between. What do you record?
APPLY: You sit on cafe Wi-Fi with a 10.0.0.0/8 address. You want "real subnetting practice." Allowed action?
APPLY: A firewall object uses 172.32.1.0/24 labeled "RFC1918 servers." What is wrong, and why does it matter?
APPLY: True or False: Mask 255.255.255.0 is /24, that /24 contains 256 IPv4 addresses, and subnetting exists partly so broadcast domains and security zones can be smaller than one giant flat LAN.