Network+ Course Notes

Network models help identify where a problem or protocol belongs. The OSI model separates communication into seven layers, while the TCP/IP model groups similar functions into fewer layers such as application, transport, internet, and network access. Network+ questions often ask you to map OSI Network Layer behavior to TCP/IP Internet Layer behavior or to separate transport functions from application protocols.

• Do not memorize OSI layers without mapping them to TCP/IP behavior and real protocols.

• If the item names ports, tie SMTP, HTTP, HTTPS, SSH/SFTP, and RDP to their usual numbers.

VLANs separate Layer 2 broadcast domains on the same switching infrastructure. An access port belongs to one VLAN, while a trunk carries traffic for multiple VLANs between switches or to devices that understand VLAN tags. Network+ questions often test that VLANs segment traffic logically without requiring a separate physical switch for each network.

• Do not confuse a native VLAN with a parking VLAN; native VLAN handles untagged trunk traffic, while parking VLAN isolates unused ports.

• If the question asks for multiple VLANs over one link, choose trunking.

Network documentation lets teams understand what exists before they troubleshoot or change it. Physical diagrams show devices, cabling, racks, and ports; logical diagrams show VLANs, subnets, routing, and service relationships. Rack diagrams document equipment placement, power, and cabling density in cabinets.

• A physical diagram shows devices and cabling, while a logical diagram shows subnets, VLANs, and routing relationships.

• If the question asks what is installed where, choose rack or physical diagrams.

DDoS attacks overwhelm a target with traffic or requests, but they can also be used as distraction attacks. While attention is on availability loss, attackers may attempt fraud, intrusion, or data theft elsewhere. Network+ questions may ask you to recognize that a denial-of-service event can hide a secondary attack.

• IDS alerts on suspicious traffic, while IPS can block traffic inline.

• If management access is the issue, look for management plane ACLs and disabled unused services.

Troubleshooting methodology gives structure to network repair. Start by identifying the problem, gathering symptoms, and determining what changed. Then establish a theory, test the theory, create an action plan, implement the fix, verify full functionality, and document findings so the same issue can be recognized later.

• A failed ping is a clue, not proof that the destination is down, because firewalls may block ICMP.

• Follow the troubleshooting methodology order before jumping to fixes.