CCNA Flashcards
(135 cards)
1
Q
What do OSI layers mean? How many layers does the OSI model have?
A
OSI (Open Systems Interconnection) reference model for a network architecture. It has 7 layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application.
2
Q
What is the Physical layer responsible for?
A
The Physical layer is responsible for the bit stream.
3
Q
What is the Data Link layer responsible for?
A
The Data Link layer is responsible for moving frames from one hop (node) to the next (Hop-to-hop or node-to-node delivery).
4
Q
What are the functions of the Data Link layer?
A
Framing, Physical Addressing (MAC Address), LLC sublayer, Hop-to-hop error & flow control.
5
Q
What protocols are examples of the Data Link layer?
A
Examples include HDLC, PPP, and Ethernet Protocols.
6
Q
What is the Network layer responsible for?
A
The Network layer is responsible for the delivery of individual packets from the source host to the destination host.
7
Q
What logical addressing does the Network layer use?
A
It uses IPv4, IPv6, IPX, APPLETALK.
8
Q
What is the Transport layer responsible for?
A
The Transport layer is responsible for providing reliable and efficient transport of packets (End-to-End).
9
Q
What are examples of Transport layer protocols?
A
Examples include TCP (Transmission Control Protocol) and UDP (User Datagram Protocol).
10
Q
What is the difference between TCP and UDP?
A
TCP is connection-oriented and ensures data integrity and order, while UDP is connectionless and does not guarantee delivery or order.
11
Q
What does the Session layer do?
A
The Session layer provides services to the presentation layer to organize and manage data exchange.
12
Q
What does the Presentation layer provide?
A
The Presentation layer provides common representation of the data transferred between application layer services.
13
Q
What services does the Application layer provide?
A
Email services, web browsing services, file transfer services, remote access services, DNS, BOOTP, DHCP, and SNMP.
14
Q
What is routing?
A
Routing is the process of finding a path on which data can pass from source to destination, done by routers.
15
Q
What are the types of routes in routing?
A
Static Route, Default Route, and Dynamic Route.
16
Q
What is Static Route ?
A
This route is also known as a non-adaptive route. It is either directly configured on an active interface of the router or manually added to the routing table by an administrator.
17
Q
What is Default Route ?
A
In this, the router is configured to send all packets towards a single router, and it does not matter whether or not it belongs to a specific network. It is especially used when networks deal with a single exit point.
18
Q
What is Dynamic Route ?
A
This route is also known as the adaptive route. It makes automatic adjustments of the routes as per the current state of the route in the routing table and also uses routing protocols to find network destinations.
19
Q
What is Switching?
A
Switching enables interconnecting links to form a larger network, working at the Data Link layer.
traffic control
20
Q
What is the advantage of using switches?
A
Switches efficiently forward data frames to the appropriate port instead of broadcasting on all ports.
21
Q
What are the two types of IP addresses?
A
IPv4 and IPv6.
22
Q
What does a Window mean in networking?
A
A Window refers to the number of segments allowed to be sent before an acknowledgment is received.
23
Q
What causes network congestion?
A
Network congestion occurs when too many users try to use the same bandwidth.
24
Q
What does the LLC sublayer do?
A
The LLC sublayer provides optional services to an application developer, including flow control and error correction.
25
What memories are used in a CISCO router?
NVRAM stores the startup configuration file, DRAM stores the executing configuration file, and Flash Memory stores the Cisco IOS.
26
What is the difference between User Mode and Privileged Mode?
User Mode is for regular tasks, while Privileged Mode includes all User Mode options plus configuration capabilities.
27
What is latency?
Latency is the time delay from when a network device receives a data frame to when it sends it out again.
28
What is MTU? What is the default size?
MTU stands for Maximum Transmission Unit, referring to the maximum packet size that can be sent without fragmentation.
29
What's the difference between data encapsulation and data de-encapsulation?
Encapsulation adds headers as data moves down the OSI layers, while de-encapsulation removes headers as data moves up.
30
What is CDP?
CDP stands for Cisco Discovery Protocol, a layer 2 protocol used to identify device details.
31
What are the two types of ports of switches?
Access Port, Trunk Port and Tunnel Ports
32
Access Port
It connects network hosts to a single VLAN and only carries the traffic of one VLAN. In this, traffic is sent and received in native format without any VLAN tagging. Access ports are basically used to connect switch ports with computers with a minimum of 10 Mbps speed.
33
Trunk Port
It generally connects to another switch and is able to interact with several other VLANs. By default, it is a member of all VLANs in the VLAN database. The trunk port is basically used for multiple connections between the switch to switch and switch to routers
34
Tunnel Ports
designed for service providers who carry traffic of multiple customers across their networks and are required to maintain the VLAN and Layer 2 protocol configurations of each customer without impacting the traffic of other customers. Both 802.1Q tunneling and Layer 2 protocol tunneling are supported
35
What is frame relay?
Frame relay is a WAN protocol providing connection-oriented communication by creating virtual circuits.
36
VLAN
VLAN (Virtual Local Area Network) is basically a logical group of workstations, services, or network devices that communicate with one another on a separate physical LAN.
37
What advantage does VLAN provide?
VLAN improves network performance and security by logically grouping devices on separate physical LANs.
It also allows several networks to work virtually as if they were a LAN sharing a single broadcast domain.
* Removes latency and traffic load on the network
* Saves network resources and increases network efficiency
* Reduces IT cost and the incidence of collisions
* Improve network security and performance
* Ensure network flexibility and provide easier management
* Make it easier to relocate a network or a network device
* Increase the number of broadcast domains while decreasing the size of broadcast domains.
* Establish broadcast domains in switched networks.
38
What's the difference between a public IP and a private IP?
Public IP is used on public networks, while Private IP is used within a private network.
39
What is a MAC address?
A MAC address is the identification used to depict a media access control layer in a network's architecture.
40
What is subnetting?
Subnetting creates smaller networks from a larger parent network.
41
What are the major states in a switch?
Forwarding State, Blocking State, Disabled, Listening, Learning.
42
What's the difference between a static IP and a dynamic IP?
Static IP addresses are manually assigned, while dynamic IP addresses are provided by a DHCP server.
43
What are the two types of cables used in networking?
Cross cable and straight cable.
44
What do you mean by OSPF?
OSPF stands for Open Shortest Path First, a link-state routing protocol for IP networks.
45
What is EIGRP?
EIGRP stands for Enhanced Interior Gateway Routing Protocol, used for automating routing decisions.
46
How does RIP differ from IGRP?
RIP is a distance vector protocol using hop count, while IGRP uses bandwidth, load, and delay metrics.
47
What does BPDU Guard mean in a switch?
BPDU Guard protects the Layer 2 Spanning Tree Protocol topology against BPDU-related threats.
48
What is VLSM?
VLSM stands for Variable Length Subnet Mask, allowing varying sizes of subnet masks.
49
What is Bandwidth?
The maximum amount of data transmitted over an internet connection in a given time.
50
What are segments?
Segments are sections of a data stream ready for transmission at the Transport Layer.
51
What are the five types of passwords used in securing a CISCO router?
Enabled, Enable Secret, and others not specified.
52
What are segments?
Segments are sections of a data stream that comes from the upper OSI layers and are ready for transmission towards the network. Segments are the logic units at the Transport Layer.
53
Differentiate full-duplex from half-duplex.
Full-duplex communication allows data to be sent and received at the same time, eliminating the risk of collisions. Half-duplex allows data transmission in both directions, but only one direction at a time, which can lead to collisions.
54
What is the difference between a switch, hub, and router?
A Hub is a simple networking device that connects computers in a LAN but does not filter data. A switch connects devices in a network and sends messages to specific nodes, increasing security and reducing collisions. A Router connects multiple networks and determines the best path for data.
55
How does cut-through LAN switching work?
Cut-through switching is a method where the switch starts forwarding a frame as soon as it reads the destination MAC address, reducing latency compared to store-and-forward switching.
56
How do you configure a Cisco router to route IPX?
To configure a Cisco router for IPX, enable IPX routing with 'Router(config)# ipx routing' and enable IPX on interfaces with 'Router(config)# interface Ethernet0' followed by 'Router(config-if)# ipx network AABB'.
57
What are the different IPX access lists?
There are three main types of IPX access lists: Standard IPX access lists (800–899), Extended IPX access lists (900–999), and SAP access lists (1000–1099).
58
What are the advantages of a layered model in the networking industry?
The layered model provides modularity, interoperability, simplified troubleshooting, standardization, flexibility in development, and educational clarity.
59
What’s the easiest way to remotely configure a router?
The most convenient way to configure a router remotely is to use the Cisco AutoInstall Procedure, provided the router is connected to the WAN or LAN.
60
What are packets?
A data packet is a unit of data made into a single package for transmission over a network, containing essential information like email messages and website data.
61
What are some benefits of LAN switching?
Benefits of LAN switching include allowing full duplex data transmission, media rate adaptation, and easy and efficient migration.
62
What is Route Poisoning?
Route Poisoning is the process of inserting a table entry of 16 to a route, making it unreachable to prevent problems caused by inconsistent updates.
63
How do you find valid hosts in a subnet?
To find valid hosts in a subnet, use the equation 256 minus the subnet mask.
64
Why is network segmentation a good idea when managing a large network?
Network segmentation helps ease network traffic and ensures high bandwidth availability, improving performance.
65
What identifying information can be accessed in a CISCO router?
The hostname and the interfaces, which refer to the router ports, can be accessed.
66
What command must be used to delete the configuration data stored in NVRAM?
The command to delete the configuration data stored in NVRAM is 'erase startup-config'.
67
What command must be used on the branch router prior to traffic being sent?
The command to be used prior to sending traffic is not specified in the provided text.
68
What factor must be considered in determining the OSPF router ID?
The highest IP address of any physical interface must be considered.
69
What is the size of an IP address?
The size of an IP address is 32 bits for IPv4 and 128 bits for IPv6.
70
In how many ways can you access the router?
You can access the router via Telnet (IP), AUX (Telephone), and Console (Cable).
71
What command do we give if the router IOS is stuck?
The command is 'Cntrl+Shift+F6 and X'.
72
What route entry will be assigned to a dead or invalid route in case of RIP?
In the case of RIP, 16 hops will be assigned to a dead or invalid route, making it unreachable.
73
What is Circuit Switching?
Circuit switching is a method that establishes a dedicated channel for communication, initially designed for voice transfer, and implemented at the Physical Layer.
74
What is Packet Switching?
Packet switching is a method of grouping data into packets for transmission over a digital network, designed for data transfer and implemented at the Network Layer.
75
Explain the difference between a broadcast domain and a collision domain.
A Broadcast Domain is a logical set of reachable systems without a router, while a Collision Domain is a part of a network where packet collisions can occur.
76
Name different types of networks.
1. Server-based network: Centralized server provides services to clients.
2. Peer-to-Peer network: Nodes are connected to each other directly.
77
Explain the use of the ping command.
Ping is a tool used to test whether a particular host is reachable across an IP network.
78
Explain round-trip time.
Round-trip time is the time required for a packet to travel from a source to a destination and back again.
79
How many VTP modes are in a switch? Name them.
There are three VTP modes in a switch: server, client, and transparent.
80
What is the primary function of the Transport Layer in the OSI model?
It ensures reliable data transfer between hosts.
## Footnote
This layer (Layer 4) handles segmentation, flow control, and error correction. Protocols: TCP and UDP.
81
Which OSI layer corresponds to the Internet Layer in the TCP/IP model?
The Network Layer (Layer 3).
## Footnote
The Internet Layer in TCP/IP handles routing and IP addressing, just like OSI’s Layer 3.
82
At which OSI layer do routers operate, and why?
Layer 3 (Network Layer).
## Footnote
Routers make forwarding decisions based on IP addresses, which reside in Layer 3.
83
Which layer of the OSI model is responsible for MAC addressing and framing?
Data Link Layer (Layer 2).
## Footnote
It provides physical addressing and prepares data for transmission over the physical medium.
84
What is the main difference between the TCP/IP and OSI models in terms of layer count?
OSI has 7 layers, TCP/IP has 4 (or 5 in some variations).
## Footnote
TCP/IP combines the OSI Application, Presentation, and Session layers into one.
85
In which OSI layer does DNS operate?
Application Layer (Layer 7).
## Footnote
DNS resolves domain names to IP addresses and is considered an application-layer service.
86
Which layer is responsible for establishing, maintaining, and terminating sessions between applications?
Session Layer (Layer 5).
## Footnote
It manages sessions or dialogs between computers.
87
If you are troubleshooting packet delivery and suspect an issue with port numbers, which OSI layer should you focus on?
Transport Layer (Layer 4).
## Footnote
This layer is responsible for port numbers and managing end-to-end communication.
88
What OSI layer would be responsible for SSL/TLS encryption?
Presentation Layer (Layer 6).
## Footnote
This layer deals with data encryption, decryption, compression, and translation.
89
Which TCP/IP layer is responsible for device-to-device delivery within a local network?
Network Access Layer.
## Footnote
It corresponds to the OSI Data Link and Physical layers and handles local delivery.
90
Explain the use of ‘ping’ command?
Packet Internet Groper is a computer network tool that is used to test whether a particular host is reachable across an IP network.
91
Explain ‘round-trip time’?
Round-trip time, or round-trip delay, is the time required for a packet to travel from a specific source to a specific destination and back again.
92
How many VTP modes are in a switch? Name them.
server, client, and transparent.
93
Explain the difference between static and dynamic IP addressing?
Dynamic IP addresses can change every time a device connects to the internet. Static IP addresses are reserved. They do not change with time.
94
What is ‘subnet’?
Subnets are used in IP networks to optimize the performance of a network because it reduces traffic by breaking a large network into smaller networks.
95
Which IP address is used for loopback address and why?
127.0.0.1 is used for the loopback address.
## Footnote
A loopback address is a special IP address that a network administrator uses to treat the local machine as a remote machine. It is also used for local testing.
96
How to choose DR in OSPF?
Highest priority, Highest router ID, Highest IP address.
97
Can a bridge divide a network into multiple smaller sections?
Yes, a bridge can divide a network into smaller collision domains, but not broadcast domains.
98
What is the difference between tracert and traceroute?
Both tracert (used in Windows) and traceroute (used in Linux/Unix/Mac) are diagnostic tools used to trace the path that packets take from a source to a destination.
99
What is the difference between CSMA/CD and CSMA/CA?
CSMA/CD is used in wired Ethernet networks. CSMA/CA is used in wireless networks (like Wi-Fi).
100
What is the difference between communication and transmission?
Transmission refers to the physical process of sending data from one device to another over a medium. Communication refers to the complete exchange of information between devices or people.
101
What is Topology in CCNA?
It is an arrangement of various elements (links, nodes, etc.) of a computer network in a specific order.
102
What is RAID in CCNA?
RAID stands for Redundant Array of Independent Disks.
## Footnote
RAID levels provide various facilities like performance, cost, reliability, etc.
103
What is the point-to-point protocol in CCNA?
The point-to-point protocol is an industry standard suite of protocols which uses the point-to-point link to transport multiprotocol datagram.
104
What is the difference between ARP and RARP?
ARP maps a 32-bit logical address to a 48-bit physical address. RARP maps a 48-bit physical address to a 32-bit logical address.
105
You are given the IP address 192.168.10.0/26. How many valid hosts can this subnet support?
62 valid hosts.
## Footnote
A /26 subnet has 64 IP addresses. Subtract 2 for network and broadcast addresses: 64-2 = 62.
106
What is the broadcast address for 192.168.10.0/26?
192.168.10.63.
## Footnote
The broadcast address is the last IP in the subnet.
107
What is the 3rd valid host address for 192.168.10.0/26?
192.168.10.3.
## Footnote
First valid host: 192.168.10.1. Third valid host: 192.168.10.3.
108
Given the IP address 172.16.35.123/20, what is the subnet mask in dotted decimal?
255.255.240.0.
## Footnote
/20 means 20 bits for the network.
109
What subnet is the IP address 172.16.35.123/20 part of?
172.16.32.0/20.
## Footnote
172.16.35.123 lies between 172.16.32.0 - 172.16.47.255.
110
What is the range of usable IPs for 172.16.35.123/20?
172.16.32.1 to 172.16.47.254.
## Footnote
Subtract network and broadcast addresses from 172.16.32.0/20.
111
You have a requirement to create 29 subnets, each supporting 100 hosts. What is the minimum subnet mask you can use?
/25.
## Footnote
/25 provides 128 IPs, 126 usable. Enough for 100 hosts.
112
What class does the IP address 10.0.0.0 belong to?
Class A.
## Footnote
10.0.0.0 falls in 1.0.0.0 to 126.0.0.0 (Class A).
113
How many total IPs are wasted in the configuration for 29 subnets?
812 IPs wasted.
## Footnote
Each /25 subnet has 128 IPs. 29 × 128 = 3712. Only 2900 used.
114
What is the difference between OSPF and EIGRP in terms of convergence time, scalability, and metric calculation?
OSPF is open standard, uses cost (based on bandwidth), and has slower convergence but better scalability. EIGRP is Cisco-proprietary, uses a composite metric (bandwidth, delay), and converges faster in smaller networks.
115
Explain how STP (Spanning Tree Protocol) prevents loops in a network.
Root bridge is the central point. BPDUs (Bridge Protocol Data Units) are exchanged to elect it.
116
How can you force a specific switch to become the root?
Set a lower priority using: 'spanning-tree vlan X priority 0'.
117
You observe that a switch port is flapping between forwarding and blocking states. What could be the cause?
Possible STP loop, duplex mismatch, or physical issue.
118
How would you troubleshoot a switch port flapping?
Check cable, port settings, run 'show spanning-tree', enable BPDU Guard.
119
What is the effect of the command ip route 0.0.0.0 0.0.0.0 Serial0/0 on a router?
It sets a default route to forward all packets to the Serial0/0 interface.
120
You configure OSPF on a router using the command router ospf 1 followed by network 192.168.1.0 0.0.0.255 area 0. What does this do?
It enables OSPF process 1 and advertises the 192.168.1.0/24 network in area 0.
121
What is the result of configuring the following ACL on a router?
It blocks Telnet traffic while allowing all other IP traffic.
122
How does PortFast affect STP behavior on access ports?
It immediately brings the port to the forwarding state, bypassing listening and learning states.
123
In which scenario would you use NAT Overload (PAT)?
When you need multiple internal devices to access the internet using a single public IP.
124
What is the difference between access and trunk ports on a switch?
Access ports carry traffic for one VLAN, while trunk ports carry traffic for multiple VLANs using tagging.
125
How do you prevent VLAN hopping attacks?
Disable DTP on trunk ports, use switchport mode access on access ports.
126
You want to block all HTTP access from 192.168.1.0/24 to 10.1.1.0/24 but allow everything else. What ACL would you use?
The first line blocks HTTP (port 80), and the second permits all other traffic.
127
What is the purpose of a CSU/DSU in a WAN connection?
It connects a router’s serial interface to a digital WAN service like T1 or E1.
128
What is the key difference between PPP and HDLC?
PPP supports authentication (PAP/CHAP) and multi-protocol, while HDLC is Cisco-proprietary and limited.
129
What is the difference between Static NAT and Dynamic NAT?
Static NAT maps one private IP to one public IP. Dynamic NAT maps a private IP to any available public IP from a pool.
130
What is the purpose of using SSH over Telnet?
SSH encrypts the entire session, making it secure; Telnet sends data in plaintext.
131
A user cannot SSH into a switch. What are possible reasons?
SSH not enabled, no domain name set, RSA keys not generated.
132
What happens if two switches in a network have the same bridge priority and MAC address?
This is extremely rare; tie-breakers wouldn’t work properly, potentially leading to instability in STP.
133
A port is stuck in the err-disabled state. What are possible causes and how do you recover it?
Causes include port security violations, BPDU guard, or link flaps.
134
Public IP
It is used on public networks.
It is usually assigned by a Service provider or IANA.
It is generally used to communicate outside the network.
It can be known by searching “what is my IP” on google.
Its scope is global.
These come with a cost and are controlled by ISP.
It is routable and therefore, communication among different users is possible.
It can be any number not included in the reserved private IP address range.
Example: 202.60.23.1
135
private IP
It is mostly used within a private network or LAN to connect securely with other devices within the same network.
It is usually assigned by a LAN administrator.
It is generally used to communicate within the same network.
It can be known by typing “ipconfig” on the command prompt.
Its scope is local to the present network.
These are free of cost and are used to load network OS.
It is not routable and therefore, communication among different users is not possible.
Address ranges to be used by private networks are:
Class Range
A 1-126 Network Host Host Host
B 127-191 Network Network Host Host
C 192-223 Network Network Network Host
D 224-239
E 240-254
