ACL – Access Control List
A set of rules that control network traffic and access to devices.
APIPA – Automatic Private IP Addressing
Assigns a default IP (169.254.x.x) when DHCP is unavailable.
ARP – Address Resolution Protocol
Maps IP addresses to physical MAC addresses on a local network.
AS – Autonomous System
A collection of IP networks under a single administrative domain.
BGP – Border Gateway Protocol
A protocol used to exchange routing information between autonomous
systems.
CBWFQ – Class-Based Weighted Fair Queuing
A QoS method that provides bandwidth to different classes of traffic.
CDP – Cisco Discovery Protocol
A Cisco protocol that discovers directly connected Cisco devices.
CIDR – Classless Inter-Domain Routing
Allows IP address and subnet mask flexibility beyond classful
addressing.
DHCP – Dynamic Host Configuration Protocol
Automatically assigns IP addresses to devices on a network.
DNS – Domain Name System
Translates domain names (e.g., google.com) into IP addresses.
DUAL – Diffusing Update Algorithm
Used by EIGRP to determine the best path and backup paths.
EIGRP – Enhanced Interior Gateway Routing Protocol
A Cisco routing protocol that uses bandwidth and delay for metrics.
FTP – File Transfer Protocol
Transfers files between computers over a network.
HTTP – Hypertext Transfer Protocol
A foundational protocol for communication on the World Wide Web
ICMP – Internet Control Message Protocol
Sends error messages and operational information (used by ping).
IP – Internet Protocol
Delivers packets from source to destination using logical addresses.
MAC – Media Access Control
A unique identifier assigned to network interfaces for communications.
MPLS – Multiprotocol Label Switching
Directs data from one node to another based on short path labels.
NAT – Network Address Translation
Translates private IP addresses to a public IP address and vice versa.
NIC – Network Interface Card
Hardware that connects a computer to a network.
OSI – Open Systems Interconnection
A conceptual model that standardizes network communication into 7
layers.
OSPF – Open Shortest Path First
A link-state routing protocol that uses cost as a routing metric.
PAT – Port Address Translation
A type of NAT that maps multiple private IPs to a single public IP using
ports.
QoS – Quality of Service
Techniques to manage network traffic and ensure performance for
critical applications.
RDP – Remote Desktop Protocol
A Microsoft protocol that allows remote access to another computer.
RIP – Routing Information Protocol
A distance-vector routing protocol with a max hop count of 15.
RSTP – Rapid Spanning Tree Protocol
An improved version of STP for faster convergence.
SMTP – Simple Mail Transfer Protocol
The standard protocol used for sending emails across networks
SSH – Secure Shell
Provides secure access to remote devices over an unsecured network.
STP – Spanning Tree Protocol prevents Ethernet network loops by
blocking redundant paths.
TCP – Transmission Control Protocol
A connection-oriented protocol that ensures reliable delivery of data.
Telnet – Telecommunications Network
Allows remote login to another computer, unencrypted.
UDP – User Datagram Protocol
A connectionless protocol used for fast transmissions like video or DNS.
VLAN – Virtual Local Area Network
Segments a network logically to separate broadcast domains.
VLSM – Variable Length Subnet Masking
Allows subnets of different sizes within the same network.
VTP – VLAN Trunking Protocol
Cisco protocol to manage VLANs across switches.
WFQ – Weighted Fair Queuing
A QoS scheduling algorithm that assigns bandwidth fairly among flows.
Wi-Fi – Wireless Fidelity
A technology for wireless local area networking using radio waves.
Q&A
1. Troubleshooting Fundamentals
Q: A user can’t connect to the internet. What steps do you take to
troubleshoot?
A:
1. Check physical connections (cable or Wi-Fi)
2. Verify IP address with ipconfig
3. Ping default gateway to check local network
4. Ping public IP (e.g., 8.8.8.8)
5. Check DNS with nslookup google.com
6. Restart network adapter / router if needed
Q: How do you diagnose a slow network?
A:
Use ping to check latency
Use tracert to find slow hops
Check for congestion or interference (on Wi-Fi)
Review bandwidth usage and running background apps
Q: What’s the difference between a hub, switch, and router?
A:
Hub: Broadcasts data to all ports
Switch: Sends data only to the destination MAC address
Router: Connects different networks, assigns IPs, routes data
Q: A printer isn’t working on the network. What do you do?
A:
Ensure it’s powered on and connected
Check IP config of printer
Ping printer IP
Reinstall driver or reset spooler
Q: What if ping works but DNS fails?
A:
DNS server may be unreachable or misconfigured
Try using another DNS (like 8.8.8.8)
Restart DNS client service
2. Networking Basics
Q: What is an IP address?
A: Logical identifier for a device on a network; used to route traffic.
Q: Difference between static and dynamic IP?
A: Static is manually assigned; dynamic is given by DHCP.
Q: Difference between public and private IP?
A:
Public: Routable on the internet
Private: Used inside LANs (e.g., 192.168.x.x)
Q: What is DHCP? What happens when it fails?
A: DHCP assigns IPs automatically. If it fails, device may use APIPA
(169.254.x.x) or stay unconnected.
Q: What is a default gateway?
A: The router IP used to leave the local network.
Q: What is DNS?
A: Domain Name System resolves domain names to IP addresses.
3. OSI Model & Layers
Q: Explain the OSI model.
A:
1. Physical
2. Data Link
3. Network
4. Transport
5. Session
6. Presentation
7. Application
Q: Which layer causes web issues?
A: Layers 3 (Network), 4 (Transport), or 7 (Application)
Q: What layer is a switch? A router?
A:
Switch: Layer 2
Router: Layer 3
4. Protocols & Ports
Q: TCP vs UDP?
A:
TCP: Reliable, connection-oriented
UDP: Unreliable, faster
Q: Ports:
SSH: 22
FTP: 21
DNS: 53
SMTP: 25
DHCP: 67/68
Q: How does ARP work?
A: ARP maps IP addresses to MAC addresses.
5. System Tools & Commands
Q: How to remote into a user’s PC?
A: Use RDP (Windows), VNC, AnyDesk, or TeamViewer
Q: How to check IP and gateway in Windows?
A: Use ipconfig in Command Prompt
Q: Tools to troubleshoot a network?
A: ping, tracert, ipconfig, nslookup, netstat, Wireshark
Q: Telnet vs SSH?
A: Telnet is unencrypted; SSH is encrypted
6. Security Basics
Q: How to secure Wi-Fi?
A: Use WPA2/WPA3, disable WPS, use strong passwords, limit MACs
Q: What is a firewall?
A: Security system that filters traffic based on rules
Q: Symmetric vs Asymmetric encryption?
A:
Symmetric: Same key for encrypt/decrypt
Asymmetric: Public/private key pair
Q: How to secure a switch port?
A: Use port security:
switchport port-security
switchport port-security maximum 1
switchport port-security mac-address sticky
7. Real-World Scenarios
Q: Can't open a file server?
A:
Check if server is online
Ping the server
Check share permissions and firewall
Q: Replaced network cable but issue persists?
A:
Try different port/NIC
Test cable with a tester
Reboot device and verify config
Q: Device not getting IP address?
A:
Check if DHCP is running
Verify cable or Wi-Fi
Manually assign IP to test
8. Behavioral Tech Questions
Q: Have you dealt with an angry client?
A: Yes, I remained calm, listened to their issue, reassured them, and
provided a solution while keeping them updated.
Q: What if you don’t know the solution?
A: I document the issue, research it, consult with senior staff or vendor docs,
and follow up with a verified fix.
Q: Do you document problems/solutions?
A: Always. It helps in future troubleshooting and knowledge sharing.
