Transport Layer
TCP and UDP both use this field to identify application processes.
Port number
Which protocol resolves names to IPs before a web session begins?
DNS
The first line of defense that separates a private LAN from the Internet.
Firewall
Device operating at OSI Layer 2 that separates collision domains.
Switch
Command to verify end-to-end connectivity.
ping
A web server uses port 80. What is the destination port number in the client-to-server segment?
80
HTTP and HTTPS operate at this OSI layer.
Application layer (Layer 7)
A user receives an email urging immediate password change on a fake site. Type of attack?
Phishing
What is required to maintain a high degree of reliability and eliminate single points of failure?
Redundancy
A PC can ping others on the same subnet but not external networks. What’s missing?
Default Gateway
A file download starts twice because acknowledgments were lost. Which TCP feature prevents duplicates?
Sequence numbers with acknowledgment tracking
POP3 and IMAP both retrieve mail; which one keeps messages on the server by default?
IMAP
Which secure protocol should replace Telnet for remote device access?
SSH
Protocol that prevents loops when redundant switch links exist.
Spanning Tree Protocol (STP)
A router shows correct IP addresses but no traffic passes between LANs. What’s the likely issue?
IP routing disabled
How does UDP handle dropped datagrams?
It doesn’t — loss detection is left to the application.
Which application layer protocol securely transfers files using encryption?
SFTP
Switch feature that limits access by MAC address.
Port security
Layer 3 device combining switching and routing capabilities.
Multilayer switch
Users report slow access to websites, but internal pings are fine.
DNS server unreachable or misconfigured.
During congestion, TCP lowers throughput using this mechanism.
Congestion window
In HTTPS, which protocol establishes the secure channel before HTTP data is exchanged?
TLS (Transport Layer Security)
Security principle that grants users only the permissions they need.
Least privilege (or RBAC)
Three-tier network design model layers.
Access, Distribution, Core
After connecting two switches, VLAN traffic doesn’t cross. What should be verified first?
Trunk configuration and allowed VLANs