Network+ (N10-009) · ELI Explains IP Addresses (book)
Commonly Confused Concepts
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These concept pairs look or sound similar but serve different functions. Use this section to quickly distinguish them.
The college version
Private vs Public IP Addresses
Private: works inside your local network only, not routed on the internet (e.g., 192.168.1.5). Uses NAT to reach the internet. Public: globally unique, routable everywhere on the internet (e.g., your router's ISP-assigned address). Key difference: Can the address be reached directly from the internet? Private = no. Public = yes.
Static vs Dynamic IP Addresses
Static: manually configured, stays the same until someone changes it. Used for servers, printers, infrastructure. Dynamic: automatically assigned by DHCP, may change when the lease expires. Used for laptops, phones, client devices. Key difference: Does the address change on its own? Static = no, it's fixed. Dynamic = yes, it's leased.
Broadcast vs Multicast vs Anycast
Broadcast: one-to-all. One sender, every device on the local network receives it. IPv4 only. Multicast: one-to-many. One sender, only subscribed group members receive it. Anycast: one-to-nearest. Multiple devices share the same address; traffic goes to the closest one. Key difference: How many devices receive the traffic — all, a subscribed group, or the closest one.
NAT vs PAT
NAT: translates private IP addresses to public IP addresses in general. Can be one-to-one or many-to-one. PAT: a specific type of NAT that uses port numbers to map many private addresses to one public address. Also called NAT overload. Key difference: PAT is the specific many-to-one-with-ports version of NAT used in nearly all home routers. All PAT is NAT, not all NAT is PAT.
Link-Local vs Loopback
Link-local: communicates with neighbors on the same network segment. Traffic can reach other devices on the link. Loopback: communicates only with itself on the same device. Traffic never leaves the device at all. Key difference: Link-local talks to local neighbors. Loopback talks only to itself — zero distance.
IPv4 vs IPv6 Notation
IPv4: 192.168.1.1 — 32-bit, four decimal octets, dots. IPv6: 2001:0db8::1 — 128-bit, eight hex groups, colons, zero-compression allowed. Key difference: Address length (32 vs 128 bits), separator character (dot vs colon), and notation conventions (decimal vs hexadecimal).
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