N10-009 cheat sheet

Exam at a glance

Domain weightings

How much of the exam each domain covers. Spend your study time in proportion — the heavier the domain, the more questions you'll see.

Key terms

OSI Model

The OSI model is a seven-layer conceptual framework (Physical, Data Link, Network, Transport, Session, Presentation, Application) that standardizes how network functions interact. Network+ uses it to classify protocols, devices, and troubleshooting steps by layer.

Subnetting

Subnetting is the practice of dividing an IP network into smaller logical subnetworks using a subnet mask or CIDR prefix. It controls broadcast domain size and address allocation, and is a core Network+ skill for IPv4 addressing.

VLAN

A VLAN (Virtual Local Area Network) is a logical segmentation of a switched network that groups devices independently of physical location. VLANs limit broadcast domains and improve security through separation, and are tagged across trunk links using 802.1Q.

Spanning Tree Protocol

The Spanning Tree Protocol (STP) is a Layer 2 protocol that prevents switching loops by blocking redundant paths while keeping a loop-free active topology. It automatically reconverges if a link fails, and is essential knowledge for switching and troubleshooting.

OSPF

OSPF (Open Shortest Path First) is a link-state interior gateway routing protocol that builds a map of the network and computes shortest paths using cost. It converges quickly and scales with areas, and is a common dynamic-routing topic on Network+.

NAT

NAT (Network Address Translation) is a technique that maps private IP addresses to one or more public addresses at a router boundary. Port Address Translation (PAT) is the common many-to-one variant that lets many internal hosts share a single public IP.

DHCP

DHCP (Dynamic Host Configuration Protocol) is a service that automatically assigns IP addresses, subnet masks, gateways, and DNS servers to clients through a discover-offer-request-acknowledge exchange. DHCP misconfiguration and IP conflicts are frequent troubleshooting scenarios.

DNS

DNS (Domain Name System) is the service that resolves human-readable domain names to IP addresses using record types such as A, AAAA, CNAME, MX, and PTR. DNS resolution failures are a common network-services issue Network+ expects you to diagnose.

802.11

Wi-Fi is the common name for the IEEE 802.11 family of standards defining wireless LAN operation across the 2.4 GHz, 5 GHz, and 6 GHz bands. Network+ covers 802.11 standard generations, channel planning, interference, and wireless security.

Zero Trust

Zero trust is a security model that assumes no user or device is inherently trusted, requiring continuous verification and least-privilege access regardless of network location. It is part of the modern security concepts Network+ N10-009 introduced.

Network Segmentation

Network segmentation is the practice of splitting a network into isolated zones — using VLANs, subnets, DMZs, or ACLs — to limit lateral movement and contain threats. It is a foundational defensive control in the Network Security domain.

Traceroute

Traceroute (traceroute on Linux, tracert on Windows) is a diagnostic tool that reveals the hop-by-hop path packets take to a destination and the latency at each hop. It is a primary tool for isolating where along a path a connectivity or latency problem occurs.

Duplex Mismatch

A duplex mismatch is a misconfiguration where two link partners disagree on half- vs full-duplex operation, causing late collisions, CRC errors, and severe throughput loss. Recognizing its symptoms is a classic Network+ physical-interface troubleshooting task.