Quick Revision

GK One-Line Question & Answer

15541+ short questions with short answers, covering every category and sub-category on the site — no long articles to scroll through. Good for a fast recap before an exam, or a few minutes of daily practice.

Looking for exam process/strategy questions instead? Try the Exam Preparation FAQ →

Computer Networks → Introduction to Computer Networks 30

802.1X supplicant is
End device requesting network access
click to copy
802.1X authenticator is
Switch or AP enforcing authentication
click to copy
802.1X authentication server is
RADIUS or TACACS+ validating credentials
click to copy
CoA in RADIUS stands for
Change of Authorization
click to copy
QoS DSCP EF value is
46
click to copy
DSCP CS6 is typically for
Network control traffic
click to copy
DSCP CS7 is for
Network control routing protocols
click to copy
DSCP 0 (CS0) is called
Best Effort or Default
click to copy
LLQ combines strict PQ for real-time with
WFQ for other traffic
click to copy
WRED drops packets
Probabilistically before buffer fills based on DSCP
click to copy
Policing drops excess traffic while shaping
Buffers and smooths excess traffic
click to copy
CIR stands for
Committed Information Rate
click to copy
WFQ provides
Weight-based proportional bandwidth allocation
click to copy
CBWFQ stands for
Class-Based Weighted Fair Queuing
click to copy
Multi-mode fiber modal dispersion is caused by
Multiple light modes taking different paths
click to copy
Single-mode fiber eliminates modal dispersion by
Using tiny core allowing only one light mode
click to copy
Chromatic dispersion in fiber is
Different wavelengths traveling at different speeds
click to copy
Optical amplifier EDFA uses
Erbium-doped fiber for signal amplification
click to copy
ROADM stands for
Reconfigurable Optical Add-Drop Multiplexer
click to copy
Coherent optical uses modulation like
QAM encoding phase and amplitude for higher capacity
click to copy
Submarine cable amplifiers get power from
DC power sent over cable from landing stations
click to copy
Modern submarine cable capacity is
100+ Tbps
click to copy
FC connector is used in
High-vibration environments and test equipment
click to copy
Traceroute sends packets with increasing TTL to
Map path by collecting ICMP Time Exceeded responses
click to copy
ARP table entry timeout default is typically
2 minutes (varies by OS)
click to copy
Gratuitous ARP purpose is
Announce own IP/MAC and detect conflicts
click to copy
DNS TTL determines
How long to cache DNS record before re-querying
click to copy
DNS zone transfer uses
TCP port 53 (AXFR)
click to copy
DNS amplification uses small queries to generate
Large responses to overwhelm target
click to copy
Modified EUI-64 flips the
7th (Universal/Local) bit of MAC-derived interface ID
click to copy

Computer Networks → Switching Techniques 1

Dynamic VLAN assignment in 802.1X is done by
RADIUS server sending VLAN attribute after authentication
click to copy

Computer Networks → Physical Layer 1

Fiber optic propagation speed is approximately
2x10^8 m/s
click to copy

Computer Networks → Network Layer 6

ICMP is used by ping to test
Host reachability and round-trip time
click to copy
ICMP redirect type 5 tells host to
Use a better route for subsequent packets
click to copy
NDP Neighbor Solicitation in IPv6 replaces
ARP requests
click to copy
IPv6 DAD sends Neighbor Solicitation to detect
Duplicate IPv6 address assignment
click to copy
IPv6 SLAAC forms address from
Network prefix from RA plus interface ID from MAC
click to copy
IPv6 privacy extensions create
Randomly changing interface IDs for privacy
click to copy

Computer Networks → Application Layer 2

DHCP lease time is
Configurable by server admin
click to copy
DHCP relay agent forwards requests from
Client to DHCP server on different subnet
click to copy