1
Q
ARP (Address Resolution Protocol)
A
Layer 2 / Network
Resolves an IP address to a MAC address on a local network
PC wants 192.168.1.20 → ARP request → MAC 00:11:22:33:44:55; related: local host, VLAN
2
Q
Bottom-Up Method
A
Troubleshooting
Start at Layer 1 and work upward to find problems
Check cables → NIC → IP → Application
3
Q
CAPWAP (Control and Provisioning of Wireless Access Points)
A
Network / Wireless
Protocol for WLAN controller to manage APs centrally
Used with centralized APs (local mode)
4
Q
D (Routing Table)
A
Routing
Route learned via EIGRP
Related: EIGRP, DUAL algorithm, dynamic routes
5
Q
DHCP (Dynamic Host Configuration Protocol)
A
Layer 7 / Application
Automatically assigns IP, subnet mask, gateway
PC gets IP 192.168.1.10
6
Q
Divide-and-Conquer Method
A
Troubleshooting
Start in the middle OSI layer and move up or down
Layer 3 test → success → check Layer 4–7
7
Q
DMVPN (Dynamic Multipoint VPN)
A
VPN / Network
Dynamic VPN allowing secure multipoint connections without manual tunnels
HQ to branch offices; often uses OSPF for routing
8
Q
Dot1Q VLAN Tag
A
Layer 2
4-byte tag in Ethernet frames for VLAN identification on trunk links
VLAN 10 frame → tag VLAN ID 10; related: trunk, subinterface, router-on-a-stick
9
Q
EIGRP
A
Layer 3 / Routing
Cisco dynamic routing protocol using DUAL algorithm for fast convergence
Routes marked D in routing table; related: DUAL, routing table
10
Q
EtherChannel
A
Layer 2 / Link
Bundles multiple physical links into one logical link
4×1Gbps → 4Gbps logical; related: trunk, STP sees as one link
11
Q
Follow-the-Path Method
A
Troubleshooting
Trace the path from source to destination to find where traffic fails
Check PC → switch → router → WAN → destination
12
Q
Full-Duplex Ports
A
Layer 1 / 2
Port can send and receive data simultaneously
Switch port configured full-duplex → doubles bandwidth
12
Q
ICMP
A
Layer 3
Protocol for network diagnostics and error messages
Ping, traceroute; related: ICMPv6, RTT
13
Q
Host / Endpoint
A
Network
Device that uses network resources
PC, server, printer; related: local host, subnet, IP
14
Q
ICMPv6
A
Layer 3
ICMP version for IPv6 networks
Neighbor Discovery, ping in IPv6
15
Q
ISL Trunk
A
Layer 2
Cisco-proprietary VLAN tagging method for multiple VLANs
Replaced by 802.1Q; related: trunk, VLAN
16
Q
Layer 3
A
OSI
Network layer; responsible for IP addressing and routing
Router decides where packets go; related: routing table, default gateway
17
Q
Local Host
A
Network
Device on the same subnet
192.168.1.10/24 → 192.168.1.20/24 is local host
18
Q
Macrobend
A
Physical / Fiber
Fiber bend that causes light to leak → signal loss
Bend fiber too sharply → link down
19
Q
Multiplexing
A
Layer 1 / Transport
Multiple signals share a single medium
VoIP + data over same fiber or cable
20
Q
NAT
A
Layer 3
Translates private IPs to public IPs for Internet access
Home router maps 192.168.1.10 → public IP; related: default gateway
21
Q
OSPF
A
Layer 3 / Routing
Open-standard link-state routing protocol
Chooses lowest-cost path; routing table letter = O
22
Q
PDU (Protocol Data Unit)
A
OSI
Data unit at each layer
Layer 1 = bits, 2 = frame, 3 = packet, 4 = segment
23
Q
PortFast
A
STP / Layer 2
Makes end-device ports skip STP delay
PC gets IP immediately; do not enable on switch-to-switch links
24
Priority Range (STP)
STP / Layer 2
STP bridge priority: 0–61440 in increments of 4096
Lower value → higher chance to be root bridge; related: BID
25
Remote Access Locations
Network
Locations where users connect from outside via VPN
Related: DMVPN, NAT
26
Routing Table
Layer 3
Router map of networks and next hops
Shows connected, static, and dynamic routes (letters: C, S, D, O)
27
Router Interface
Layer 3
Physical port on router
G0/0, G0/1
28
Router Subinterface
Layer 3
Logical interface on a physical port for VLANs
G0/0.10 → VLAN 10; related: 802.1Q, router-on-a-stick
29
Router-on-a-Stick
Layer 3 / VLAN
One router interface handles multiple VLANs via subinterfaces
VLAN 10 → G0/0.10, VLAN 20 → G0/0.20; trunk link connects switch
30
RTT (Round-Trip Time)
Network
Time for data to go to destination and back
Ping shows 30 ms → RTT = 30 ms
31
Session Multiplexing
Layer 4
Multiple sessions over a single connection
TCP multiplexing or VPN tunnels
32
Static Route
Layer 3 / Routing
Route manually configured
ip route 192.168.2.0 255.255.255.0 10.1.1.2; routing table letter = S
33
STP Bridge / Port
Layer 2
Switch running Spanning Tree Protocol; ports assigned roles (root, designated, alternate)
Prevents loops; related: PortFast, priority, BID
34
RSTP
Layer 2 / STP
Rapid STP, faster convergence and simpler port states
Successor to STP
35
Switch / SW3
Layer 2
Device that forwards frames inside a LAN
SW3 = example switch in topology; related: trunk, VLAN
36
UDP
Layer 4
Connectionless transport protocol
Used for DNS, VoIP, TFTP; no guaranteed delivery
36
Trunk
Layer 2
Switch port carrying multiple VLANs
802.1Q trunk; related: dot1Q, EtherChannel, router-on-a-stick
37
VLSM
Layer 3
Allows subnets to have variable sizes
Efficient IP usage; related: subnet mask
38
WLAN Controller
Layer 2 / Wireless
Central device that manages multiple access points
Works with CAPWAP and centralized APs
39
Default Gateway
Layer 3
Router a host sends traffic to if destination is outside local subnet
PC sends traffic to Internet → default gateway forwards it
40
MAC address
Data Link
Physical hardware identifier of a device
00:1A:2B:3C:4D:5E
40
IPv4 address
Network
Logical address used for routing packets
192.168.1.10
41
ARP
Network / Protocol
Resolves IPv4 addresses to MAC addresses on local network
arp -a shows MACs for IPs
42
IPv6 default route
Network
Route used when no other route matches
ipv6 route ::/0 2001:db8::1
43
OSPF packet types
Network / Routing
Hello, DB, LS Request, LS Update, LS Ack for exchanging routing info
Hello packets discover neighbors
44
OSPF neighbor states
Network / Routing
Sequence routers go through to become fully adjacent: Down → Init → 2-Way → ExStart → Exchange → Loading → Full
Router sees new neighbor → Full
45
OSPF cost calculation
Network / Routing
Cost = 100,000,000 / bandwidth (lower cost preferred)
100 Mbps link → Cost = 1
46
FHRP
Network / Protocol
Provides virtual gateway for hosts to survive router failure
HSRP, VRRP, GLBP
47
HSRP
Network / Protocol
Provides virtual IP as default gateway; preempt allows higher-priority router to take over
Two routers share 192.168.1.1 → standby takes over if active fails
48
Link-state protocol
Network / Routing
Routers share link info to build full network map
OSPF, IS-IS
49
Topological database
Network / Routing
Stores complete network topology for link-state protocols
OSPF router map of all routers and links
50
Default gateway
Network
Router IP hosts use to reach outside local subnet
Host 192.168.1.10 → gateway 192.168.1.1
50
Local host
Network
Device itself
ping 127.0.0.1
51
RTT
Network / Metrics
Time for a packet to go to destination and back
Ping to 8.8.8.8 → RTT = 25 ms
52
Bottom-up troubleshooting
Troubleshooting / Method
Start at physical layer and move up to isolate problems
Check cables → interfaces → IP config
52
Follow-the-path method
Troubleshooting / Method
Trace packet path to locate failure
Traceroute to find problematic router
53
Divide-and-conquer method
Troubleshooting / Method
Split network in halves to quickly isolate problem
Check first half → if OK, problem is in second half
53
Fiber issue Macrobend
Physical / Media
Large bend in fiber causing signal loss
Sharp corner bend → packet loss
53
ICMP
Network / Protocol
Sends errors and diagnostic messages
Ping, Traceroute
54
IPv4 subnet
Network / Addressing
Divides network into smaller logical networks
192.168.1.0/24 → 256 addresses
54
Router subinterfaces
Network / Interface
Logical interface for VLAN traffic
Gi0/1.10 → VLAN 10, Gi0/1.20 → VLAN 20
55
Router-on-a-stick
Network / Routing
Single physical interface with multiple subinterfaces for VLANs
Gi0/1 routes VLAN 10 and 20
56
802.1Q VLAN tag
Data Link
Adds VLAN ID to Ethernet frames
VLAN 10 → tag 0x8100 + ID
57
PortFast
Data Link / STP
Skips STP listening/learning → immediately forwards traffic
Access port to PC comes online instantly
58
TCP
Transport
Reliable, connection-oriented protocol
Web traffic, HTTP uses TCP
59
UDP
Transport
Connectionless, fast, but unreliable protocol
DNS, VoIP use UDP
60
Multiplexing
Transport / Technique
Sending multiple signals over one channel
Multiple TCP/UDP streams on one link
61
ICMPv6
Network / Protocol
IPv6 version of ICMP for diagnostics and neighbor discovery
Ping6, Neighbor Solicitation messages
62
EUI-64 interface ID
Network / Addressing
Converts MAC address to right-most 64 bits of IPv6 address
MAC 00a1-6789-abcd → IPv6 interface ID
63
Private IPv4
Network / Addressing
Addresses not routable on public Internet
10.0.0.0/8, 192.168.0.0/16
64
Public IPv4
Network / Addressing
Routable addresses on the Internet
8.8.8.8
65
Service type field (IPv4)
Network / QoS
Specifies type of traffic for QoS
Prioritize voice traffic
66
Protocols: DNS
Application
Resolves domain names to IP addresses
www.google.com → 142.250.200.78
67
Protocols: DHCP
Application
Automatically assigns IP addresses to devices
Device receives 192.168.1.10
68
Protocols: FTP
Application
File Transfer Protocol
Upload/download files
69
Protocols: TFTP
Application
Simple file transfer
Used for router/switch configs
70
Protocols: VoIP
Application
Voice over IP
Skype, Zoom calls
71
Cisco Discovery Protocol (CDP)
Data Link / Protocol
Discover neighboring Cisco devices
Shows device model, IP, port
71
Configuration file
Management
Stores device configuration
Running-config, startup-config
72
Static configuration
Management
Manually set configuration
Assign IP address manually
73
Dynamic configuration
Management
Configuration learned automatically via protocol
DHCP assigns IP
74
NAT
Network / Address Translation
Translates private → public IPs
Internal 192.168.1.10 → public 203.0.113.5
75
VLSM
Network / Subnetting
Variable-length subnet masks
192.168.1.0/25 and /26 in same network
75
PAT
Network / Address Translation
Many private IPs share one public IP using ports
10.0.0.2 → 203.0.113.5:1024
76
IPv6 header fields: Flow Label
Network / IPv6
Identifies packet flow for QoS
Video stream tagged with flow label
76
Next Header (IPv6)
Network / IPv6
Identifies type of header following IPv6 header
TCP, UDP, ICMPv6
77
Traffic Class (IPv6)
Network / IPv6
QoS priority for IPv6 packet
Prioritize voice traffic
78
Payload Length (IPv6)
Network / IPv6
Size of data portion of IPv6 packet
1280 bytes of payload
78
802.1X
Data Link / Security
Port-based authentication for network access
Wireless/802.1X switch port login
79
WPA3-Personal / WPA3-Enterprise
Data Link / Security
Wi-Fi security protocols
WPA3-Personal = home; WPA3-Enterprise = corporate
80
IoT secure onboarding (DPP)
Data Link / Security
Device provisioning and secure connection
Smart light securely joins network
81
Provider-managed VPN
Network / VPN
VPN managed by service provider
MPLS VPN
81
DOCSIS
Physical / WAN
Cable Internet standard
Comcast internet service
82
LTE
Physical / WAN
Cellular 4G technology
Mobile phone data
83
FTTx
Physical / WAN
Fiber to home/building
Google Fiber
84
ADSL
Physical / WAN
Asymmetric DSL
Internet over phone line
85
Frame Relay
Data Link / WAN
Packet-switched technology
Legacy WAN connectivity
86
DMVPN
Network / VPN
Dynamic multipoint VPN
Cisco routers form VPN dynamically
87
ATM
Data Link / WAN
Asynchronous Transfer Mode
Legacy high-speed network
88
IPsec
Network / VPN
Encrypts IP traffic
Site-to-site VPN
89
SONET / SDH
Physical / WAN
High-speed optical transport standards
Carrier backbone fiber
90
MPLS
Network / WAN
Multiprotocol Label Switching, fast path forwarding
Carrier WAN backbone
91
DWDM
Physical / WAN
Dense Wavelength Division Multiplexing
Multiple optical channels on one fiber
92
Metro Ethernet
Data Link / WAN
Ethernet service across metro area
City-wide network
93
xDSL
Physical / WAN
Family of DSL technologies
ADSL, VDSL
94
T1/E1
Physical / WAN
Dedicated leased line
1.544 Mbps T1, 2.048 Mbps E1
95
Cellular 4G
Physical / WAN
Wireless broadband
LTE mobile Internet
96
Site-to-site VPN
Network / VPN
Connects two sites securely over Internet
Office A ↔ Office B
97
Port forwarding
Network / NAT
Directs incoming traffic to specific internal host
Web server behind NAT
98
QoS tools: Link-specific
Network / QoS
Manage interface-specific traffic
Set interface bandwidth
99
QoS tools: Policing & shaping
Network / QoS
Control bandwidth usage
Limit video stream to 2 Mbps
100
QoS tools: Congestion management & scheduling
Network / QoS
Schedule packet delivery
Weighted Round Robin
101
QoS tools: Classification & marking
Network / QoS
Label packets for priority
DSCP, CoS values
102
Syslog / TACACS+ server
Management / Security
Syslog collects logs; TACACS+ authenticates users remotely
Logs sent to 10.0.0.5, TACACS+ authenticates admins
103
Console line
Management / Access
Physical access to device CLI
Plug laptop into router console port
104
Management interface
Management / Access
Dedicated interface for device management
Gi0/0 used for SSH
105
Terminal lines (vty)
Management / Access
Virtual lines for remote CLI access
vty0-4 for SSH sessions
106
SNMP trap server
Management / Monitoring
Receives SNMP alerts from devices
Monitor CPU usage or interface down events
107
MNEMONIC %LINEPROTO-5-UPDOWN
Management / Logging
Cisco log message format
Interface Gi0/1 went up/down
108
Emergency / Alert / Critical / Error
Management / Logging
Severity levels in syslog
Emergency = network unusable, Error = device failure
109
NTP client / server / master / source
Management / Time
Sync clocks across devices
Client syncs to server, server is authoritative, master = primary time source, source = interface used
110
Copy tftp running-config / startup-config
Management / Backup
Copy configuration from TFTP to device or save config
Restore router config from TFTP
111
Copy running-config startup-config
Management / Backup
Save current running configuration to startup
Prevent config loss after reboot
112
Copy startup-config tftp
Management / Backup
Save startup config to TFTP server
Backup config for disaster recovery
113
Show running-config
Management / Monitoring
Display current active configuration
show running-config
114
Show startup-config
Management / Monitoring
Display saved configuration
show startup-config
115
Show version
Management / Monitoring
Displays hardware, software, and uptime info
show version shows IOS version
116
Show config-register
Management / Monitoring
Displays boot behavior settings
Config register 0x2102 → boot normal IOS
116
XML / JSON / YAML / YANG / NETCONF
Management / Data Models
Formats and protocols for structured data / network configuration
YANG = data model, NETCONF = configuration API
117
Terraform / Ansible
Management / Automation
Tools to deploy and configure infrastructure
Terraform = build resources, Ansible = configure devices
118
Agent-based solution
Management / Monitoring
Devices run small program to report data to server
CPU stats, interface stats sent automatically
119
Logging {hostname | IP address}
Management / Logging
Configure destination for logs
Logs sent to 192.168.1.10
120
Logging trap severity / logging severity / logging level severity
Management / Logging
Define minimum severity of messages sent to syslog
Only Error and above sent
121
HTTP/1.1 / HTTP/2
Application
Web traffic protocols
Web browser → web server
122
SSH
Transport / Security
Secure remote access to CLI
ssh admin@192.168.1.1
123
RESTCONF
Application / API
RESTful network configuration protocol
Manage device config via HTTP requests
124
Spine-leaf architecture
Network / Data Center
Leaf switches connect devices, spine switches connect leafs
Low latency, redundant paths
125
Resilient network
Network / Design
Network that continues working during failures
Redundant links and devices
126
Three-tier architecture
Network / Design
Core, distribution, access layers for modular design
Campus network design
127
MR / MX / MS / MV
Wireless / Cisco
Cisco wireless devices
MR = AP, MX = security gateway, MS = switch, MV = management controller
128
SDN
Network / Architecture
Centralized controller manages network devices
Controller decides paths, devices just forward
129
Northbound APIs
SDN / Software
API from SDN controller to apps
Apps request topology or push policies
130
SD-Access campus fabric underlay network
Network / SDN
Layer 3 routed network that carries fabric traffic
Spine-leaf underlay for VXLAN
131
vBond / vManage / vSmart / WAN Edge
SD-WAN / Cisco
vBond = onboarding, vManage = management, vSmart = control, WAN Edge = data plane forwarding
Cisco SD-WAN deployment
132
Backpropagation neural networks
AI / ML
Neural network trains by sending errors backward to adjust weights
Image recognition training
133
Tokens (AI)
AI / NLP
Small pieces of text used as input for language models
“Hello world” → tokens: Hello, world
134
RAG (Retrieval-Augmented Generation)
AI / NLP
Retrieves relevant info to assist language model in generating answers
Combine knowledge base + AI response
135
Training
AI / ML
Build model from scratch with data
Train image classifier from labeled dataset
136
Fine-tuning
AI / ML
Adjust pretrained model for specific task
GPT model fine-tuned for legal documents
137
GAN (Generative Adversarial Network)
AI / ML
Two networks compete: generator vs discriminator
Generate realistic images
138
Virtualization
Network / IT
Create virtual versions of physical devices or resources
One server runs multiple virtual machines
139
Network device functional planes
Network / Device
Data plane = forwards traffic, Control plane = makes decisions, Management plane = configure/monitor
Router forwards packets, decides routes, and is managed via CLI
140
Overlay network
Network / Architecture
Virtual network over physical underlay
SD-Access fabric or VXLAN tunnels
CCNA
flashcards
Decks in class (12)
# Cards
