Interconnecting Cisco Networking Devices Part 1 (ICND1) 100-105 — Questions and Answers

Question 1: How many IPv4 addresses does a /23 subnet contain in total?

512 (Correct answer)
1024
2048
256

Correct answer: 512

A /23 has 9 host bits, so 2^9 = 512 total addresses (510 usable hosts).

Question 2: What does the EIGRP term 'feasible successor' refer to?

A backup route that meets the feasibility condition (Correct answer)
The route currently in the routing table
The router that originates a route
A route with equal cost to the successor

Correct answer: A backup route that meets the feasibility condition

A feasible successor is a backup path whose reported distance is less than the successor's feasible distance, stored in the topology table.

Question 3: What does NAT (Network Address Translation) do in networking?

It allows multiple devices to share a single public IP address (Correct answer)
It assigns IP addresses to devices.
It secures the network with encryption.
It routes traffic within a local network.

Correct answer: It allows multiple devices to share a single public IP address

NAT (Network Address Translation) is a method that allows multiple devices on a private network to share a single public IP address when accessing the internet. It translates private IP addresses to a public one, conserving public IP addresses and adding a layer of security by hiding internal network topology.

Question 4: Which device operates at Layer 1 and simply regenerates the electrical signal?

Hub (Correct answer)
Switch
Bridge
Router

Correct answer: Hub

A hub is a Layer 1 device that repeats electrical signals out all ports without any intelligence.

Question 5: A router running OSPF shows a neighbor in 'EXSTART' state for an extended time. What is the most likely cause?

OSPF process IDs are different
MTU mismatch between the two routers (Correct answer)
Area IDs are mismatched
Hello and dead timers are mismatched

Correct answer: MTU mismatch between the two routers

An MTU mismatch prevents OSPF routers from successfully exchanging DBD packets, causing the neighbor to stall in EXSTART/EXCHANGE state.

Question 6: A host cannot ping its own default gateway. After checking the cable, what should be checked next on the host?

The ARP table on the router
The host's IP address, subnet mask, and default gateway settings (Correct answer)
The switch's MAC address table
The router's routing table

Correct answer: The host's IP address, subnet mask, and default gateway settings

Incorrect IP addressing on the host, such as a wrong subnet mask, can prevent communication even with directly connected devices.

Question 7: What does it mean when a neighbor shows 'FULL/DR' in the 'show ip ospf neighbor' output?

The neighbor's LSDB is full and it acts as DR
The adjacency failed and the router is the DR
The neighbor is a fully meshed DR-only router
The neighbor is fully adjacent and is the Designated Router (Correct answer)

Correct answer: The neighbor is fully adjacent and is the Designated Router

FULL/DR means the router has reached full adjacency with that neighbor, which is the Designated Router on the segment.

Question 8: In ICND1 certification, what does redundancy in system design primarily provide?

Fault tolerance and high availability (Correct answer)
Simplified maintenance
Lower initial cost
Increased complexity

Correct answer: Fault tolerance and high availability

Redundancy provides fault tolerance by ensuring that if one component fails, backup components maintain system availability.

Question 9: Which professional attribute is most valued in ospf configuration within the ICND1 field?

Avoiding challenging situations
Accountability and commitment to standards (Correct answer)
Working in isolation
Prioritizing personal convenience

Correct answer: Accountability and commitment to standards

Accountability and commitment to professional standards build trust and ensure consistent, high-quality practice.

Question 10: Which statement BEST describes the relationship between Interconnecting Cisco Networking Devices Part 1 certification requirements and industry evolution?

Requirements evolve periodically to reflect advances in knowledge, technology, and practice standards (Correct answer)
Changes only occur when government mandates new requirements
Requirements become less stringent over time
Certification requirements never change once established

Correct answer: Requirements evolve periodically to reflect advances in knowledge, technology, and practice standards

Certification requirements evolve to keep pace with advances in professional knowledge, technological developments, and changes in practice standards. This ensures that certified professionals remain current and competent in a changing professional landscape.

Question 11: What is the role of a default gateway in networking?

It encrypts outgoing traffic.
It connects devices within the same network.
It resolves domain names to IP addresses.
It routes traffic to external networks (Correct answer)

Correct answer: It routes traffic to external networks

A default gateway is a device, typically a router, that serves as an access point for devices on a local network to communicate with external networks, such as the internet. When a device needs to send data to a destination outside its own subnet, it forwards the traffic to the default gateway, which then handles the routing.

Question 12: When documenting assessment findings in ICND1 practice, which approach is MOST appropriate?

Include only positive findings to maintain optimism
Record objective findings, measurements, and professional observations factually (Correct answer)
Use technical jargon that only experts can understand
Summarize findings verbally without written documentation

Correct answer: Record objective findings, measurements, and professional observations factually

Assessment documentation must be objective, factual, and comprehensive. Recording measurements, observations, and findings without bias ensures that the documentation is useful for decision-making and withstands scrutiny.

Question 13: What is a 'zero-day' vulnerability?

A network attack that takes zero seconds to execute
A vulnerability with no known exploits in the wild
A security flaw exploited before the vendor has released a patch (Correct answer)
A bug that only affects systems that have been running for zero days

Correct answer: A security flaw exploited before the vendor has released a patch

A zero-day vulnerability is a security flaw unknown to the vendor, meaning zero days have passed since the vendor became aware, giving no time to patch before exploitation.

Question 14: How does the ICND1 body of knowledge relate to daily professional practice?

It only applies during certification exams
It provides the foundational framework that guides decision-making and standard practices (Correct answer)
It is theoretical and has limited practical application
It is relevant only for academic research

Correct answer: It provides the foundational framework that guides decision-making and standard practices

The body of knowledge provides the foundational framework of principles, standards, and best practices that professionals use to guide their daily decision-making, ensure consistent quality, and maintain alignment with industry standards.

Question 15: What is the role of a crypto map in a Cisco IPsec VPN configuration?

It binds the transform set, peer address, and interesting traffic together and is applied to an interface (Correct answer)
It defines the encryption keys for SSH sessions
It generates RSA key pairs for certificate authentication
It configures IKE Phase 1 ISAKMP policies

Correct answer: It binds the transform set, peer address, and interesting traffic together and is applied to an interface

A crypto map ties together the ACL (interesting traffic), peer IP, and transform set, then is applied to the outbound interface to activate IPsec.

Question 16: What is the purpose of the IP address in networking?

To increase network bandwidth.
To encrypt data during transmission.
To connect devices to the internet.
To identify and locate devices on a network (Correct answer)

Correct answer: To identify and locate devices on a network

An IP (Internet Protocol) address is a unique numerical label assigned to each device connected to a computer network. Its fundamental purpose is to identify and locate these devices within the network, enabling them to communicate with each other and exchange data.

Question 17: Which SNMP version introduced strong authentication and encryption for secure network management?

SNMPv4
SNMPv3 (Correct answer)
SNMPv1
SNMPv2c

Correct answer: SNMPv3

SNMPv3 added user-based security with MD5/SHA authentication and DES/AES encryption, unlike the community-string-based v1 and v2c.

Question 18: What is the value of continuing education in ospf configuration for ICND1 professionals?

It is only needed for recertification
It keeps professionals current with evolving standards and practices (Correct answer)
It is primarily a social activity
It replaces workplace experience

Correct answer: It keeps professionals current with evolving standards and practices

Continuing education ensures professionals stay current with the latest developments, standards, and best practices in their field.

Question 19: What is the purpose of VLANs in networking?

To increase the speed of the network.
To assign IP addresses dynamically.
To segment a network into smaller, isolated networks (Correct answer)
To allow more devices to connect to the network.

Correct answer: To segment a network into smaller, isolated networks

VLANs (Virtual Local Area Networks) are used to logically segment a single physical network into multiple distinct broadcast domains. This segmentation improves network performance by reducing broadcast traffic and enhances security by isolating different groups of devices. It allows for more flexible network management without requiring separate physical hardware for each segment.

Question 20: What is the default lease time for DHCP addresses on a Cisco IOS router?

8 hours
1 hour
24 hours
1 day (Correct answer)

Correct answer: 1 day

Cisco IOS DHCP server defaults to a 1-day (86400 seconds) lease time unless configured otherwise.

Question 21: Which protocol is commonly used to dynamically assign IP addresses in a LAN?

UDP
TCP
DNS
DHCP (Correct answer)

Correct answer: DHCP

DHCP (Dynamic Host Configuration Protocol) is a network protocol specifically designed to automatically assign IP addresses and other network configuration parameters to devices on a network. This eliminates the need for manual configuration, simplifying network administration and ensuring efficient use of IP addresses. It is crucial for managing large and dynamic networks.

Question 22: What is the PRIMARY purpose of obtaining ICND1 certification in Interconnecting Cisco Networking Devices Part 1?

To demonstrate verified competency and adherence to professional standards (Correct answer)
To guarantee employment in the field
To bypass educational requirements
To satisfy a personal achievement goal

Correct answer: To demonstrate verified competency and adherence to professional standards

Professional certification demonstrates that an individual has met established competency standards through verified assessment. It provides assurance to employers, clients, and the public that the certified professional possesses the knowledge and skills required for competent practice.

Question 23: Which OSPF packet type is used to discover and maintain neighbor relationships?

DBD
LSR
Hello (Correct answer)
LSU

Correct answer: Hello

OSPF Hello packets are sent periodically to discover neighbors and verify adjacency is maintained.

Question 24: What is the most important professional competency for ICND1 certification in ospf configuration?

Deep knowledge combined with practical application skills (Correct answer)
Speed of task completion
Memorization of all reference materials
Ability to work alone exclusively

Correct answer: Deep knowledge combined with practical application skills

Professional competency requires both deep knowledge of the subject matter and the ability to apply that knowledge in practical situations.

Question 25: Which protocol is used to determine the best path for data to travel in a network?

OSPF and RIP (Correct answer)
DHCP
ARP
DNS

Correct answer: OSPF and RIP

OSPF (Open Shortest Path First) and RIP (Routing Information Protocol) are both routing protocols used by routers to determine the most efficient path for data packets to travel across a network. They achieve this by exchanging routing information with other routers and calculating the best routes based on various metrics, such as hop count or link cost. These protocols are essential for efficient data delivery in complex networks.

Question 26: A packet is destined for 172.16.5.200. Which subnet does this address belong to if the mask is 255.255.255.192?

172.16.5.192/26 (Correct answer)
172.16.5.160/27
172.16.5.128/25
172.16.5.128/26

Correct answer: 172.16.5.192/26

/26 (255.255.255.192) creates blocks of 64: .0, .64, .128, .192; address .200 falls in the .192 subnet.

Question 27: What is the effect of configuring 'ip ospf priority 0' on an interface?

The router's OSPF cost is set to zero
The interface is excluded from OSPF area 0
The router becomes the DR automatically
The router is ineligible to become the DR or BDR (Correct answer)

Correct answer: The router is ineligible to become the DR or BDR

An OSPF priority of 0 makes the router ineligible to become either the Designated Router or Backup Designated Router.

Question 28: Which protocol and port does SNMP use for NMS-to-agent queries?

TCP port 162
UDP port 161 (Correct answer)
TCP port 161
UDP port 162

Correct answer: UDP port 161

SNMP uses UDP port 161 for NMS-to-agent queries (Get/Set), while traps and informs use UDP port 162.

Question 29: A router is configured with 'ip dhcp pool SALES' and 'network 10.10.10.0 255.255.255.0'. A client on that subnet gets 10.10.10.15. The admin adds 'ip dhcp excluded-address 10.10.10.1 10.10.10.20' afterward. What happens to the existing lease for 10.10.10.15?

It is automatically moved to the next available address
It remains valid until it expires or is released (Correct answer)
The DHCP pool shuts down
It is immediately revoked

Correct answer: It remains valid until it expires or is released

Excluding an address range only prevents future assignments; existing leases remain valid until they expire or the client releases the address.

Question 30: Which CIDR prefix provides exactly 510 usable host addresses?

/22
/23 (Correct answer)
/21
/24

Correct answer: /23

A /23 has 512 total addresses (2^9), minus 2 equals 510 usable hosts.

Question 31: Which of the following is a private IP address?

64.233.160.0
172.256.256.256
8.8.8.8
192.168.1.1 (Correct answer)

Correct answer: 192.168.1.1

Private IP addresses are specifically reserved for use within local networks and are not routable on the public internet. The range 192.168.0.0 to 192.168.255.255 is one of the designated private IP address ranges, making 192.168.1.1 a classic example used in many home and office networks.

Question 32: What is the fundamental principle behind infrastructure maintenance in the ICND1 domain?

Using the newest technology exclusively
Balancing performance, reliability, and efficiency (Correct answer)
Cost minimization at all costs
Following a single vendor solution

Correct answer: Balancing performance, reliability, and efficiency

Effective technical design requires balancing performance requirements with reliability needs and operational efficiency.

Question 33: In ICND1 practice, what is the best approach to quality improvement in ipv4 and ipv6?

Copy what other organizations do without analysis
Make changes without measuring results
Use data-driven methods with measurable outcomes (Correct answer)
Wait for problems to occur before acting

Correct answer: Use data-driven methods with measurable outcomes

Data-driven quality improvement with measurable outcomes ensures that changes actually produce the intended improvements and can be verified.

Question 34: What is the default Syslog severity level that Cisco IOS logs to the console?

Warnings and above (Level 4)
Errors and above (Level 3)
Emergencies only (Level 0)
Debugging (Level 7 — all messages) (Correct answer)

Correct answer: Debugging (Level 7 — all messages)

By default, Cisco IOS sends all Syslog messages including debug (Level 7) to the console line.

Question 35: A network administrator adds 'passive-interface GigabitEthernet0/1' under RIP. What is the effect?

The interface is removed from RIP routing entirely
RIP updates are neither sent nor received on Gi0/1
RIP updates are received but not sent on Gi0/1 (Correct answer)
RIP updates are sent but not received on Gi0/1

Correct answer: RIP updates are received but not sent on Gi0/1

A passive interface suppresses RIP update transmission but still processes received updates and advertises the connected network.

Question 36: Which documentation is essential when working with network security basics in ICND1?

Marketing materials
Detailed technical specifications and as-built diagrams (Correct answer)
Only verbal notes
General descriptions without specifics

Correct answer: Detailed technical specifications and as-built diagrams

Detailed technical specifications and as-built diagrams provide the accurate reference information needed for maintenance and troubleshooting.

Question 37: What is the best practice for maintaining infrastructure maintenance performance over time?

Wait for failures before acting
Outsource all maintenance
Implement scheduled preventive maintenance (Correct answer)
Upgrade all equipment annually

Correct answer: Implement scheduled preventive maintenance

Scheduled preventive maintenance catches potential issues before they cause failures, maintaining reliability and extending equipment life.

Question 38: What does CIR (Committed Information Rate) represent in a Frame Relay network?

The minimum guaranteed bandwidth the provider will deliver on a PVC (Correct answer)
The maximum possible burst speed on the WAN link
The total bandwidth shared across all PVCs
The speed of the local access loop to the Frame Relay switch

Correct answer: The minimum guaranteed bandwidth the provider will deliver on a PVC

CIR is the guaranteed minimum bandwidth that the service provider commits to delivering on a Frame Relay PVC.

Question 39: What is the primary purpose of NAT (Network Address Translation) in a WAN environment?

To prioritize voice traffic over data
To allow private IP addresses to communicate over the public internet (Correct answer)
To load-balance traffic across multiple WAN links
To encrypt data in transit

Correct answer: To allow private IP addresses to communicate over the public internet

NAT translates private RFC 1918 addresses to public IP addresses, enabling internet access from private networks.

Question 40: What is the maximum NTP stratum value that still indicates a valid, synchronized device?

255
10
16
15 (Correct answer)

Correct answer: 15

NTP stratum values of 1-15 indicate synchronized devices; stratum 16 means the device is unsynchronized.

Question 41: What is the valid host range for the subnet 192.168.10.64/26?

192.168.10.65 – 192.168.10.126 (Correct answer)
192.168.10.65 – 192.168.10.128
192.168.10.64 – 192.168.10.126
192.168.10.64 – 192.168.10.127

Correct answer: 192.168.10.65 – 192.168.10.126

A /26 has 64 addresses; network=.64, broadcast=.127, so valid hosts are .65 through .126.

Question 42: What is the network address and prefix length for an IP address of 172.20.15.130 with a subnet mask of 255.255.255.128?

172.20.15.0/25
172.20.15.128/26
172.20.15.128/25 (Correct answer)
172.20.15.0/26

Correct answer: 172.20.15.128/25

255.255.255.128 is /25 (block of 128); 130 falls in the second block starting at .128, so the network address is 172.20.15.128/25.

Question 43: Which documentation is essential when working with infrastructure maintenance in ICND1?

Marketing materials
Only verbal notes
Detailed technical specifications and as-built diagrams (Correct answer)
General descriptions without specifics

Correct answer: Detailed technical specifications and as-built diagrams

Detailed technical specifications and as-built diagrams provide the accurate reference information needed for maintenance and troubleshooting.

Question 44: How many subnets are created when you subnet 192.168.1.0/24 using a /28 mask?

32
14
8
16 (Correct answer)

Correct answer: 16

Borrowing 4 bits from a /24 (28 - 24 = 4) creates 2^4 = 16 subnets.

Question 45: Which of the following addresses is a valid host in the subnet 10.0.0.128/25?

10.0.1.1
10.0.0.200 (Correct answer)
10.0.0.127
10.0.0.255

Correct answer: 10.0.0.200

The subnet 10.0.0.128/25 covers 10.0.0.128–10.0.0.255; only 10.0.0.200 is a valid host (not the broadcast .255).

Question 46: What is the primary function of the Routing Information Protocol (RIP)?

To assign MAC addresses.
To assign IP addresses.
To manage IP addressing.
To determine the best route based on hop count (Correct answer)

Correct answer: To determine the best route based on hop count

RIP (Routing Information Protocol) is a distance-vector routing protocol that determines the best path for data by counting the number of hops (routers) between the source and destination. The path with the fewest hops is considered the best route. While simpler to implement, RIP's reliance solely on hop count can sometimes lead to suboptimal routing decisions compared to more advanced protocols.

Question 47: A host has IP 172.16.45.200/20. What is the network address of this subnet?

172.16.48.0
172.16.32.0
172.16.45.0
172.16.40.0 (Correct answer)

Correct answer: 172.16.40.0

A /20 has a block size of 16 in the third octet; 32 ≤ 45 < 48, so the network is 172.16.40.0.

Question 48: A network administrator needs to block all Telnet access to routers from outside the corporate network. Which ACL entry accomplishes this?

deny tcp any any eq 22
deny tcp any any eq 23 (Correct answer)
deny udp any any eq 23
deny ip any any eq 23

Correct answer: deny tcp any any eq 23

Telnet operates on TCP port 23, so 'deny tcp any any eq 23' blocks all Telnet connections.

Question 49: Which protocol is used to map an IP address to a MAC address on a local network?

RARP
DHCP
ARP (Correct answer)
DNS

Correct answer: ARP

ARP (Address Resolution Protocol) is a crucial protocol used on local networks to map an IP address to its corresponding MAC (Media Access Control) address. When a device needs to communicate with another device on the same segment, it uses ARP to discover the physical MAC address associated with the destination's logical IP address.

Question 50: What is the subnet mask in dotted-decimal notation for a /20 prefix?

255.255.248.0
255.255.252.0
255.255.224.0
255.255.240.0 (Correct answer)

Correct answer: 255.255.240.0

A /20 means 20 bits are set to 1: the first two octets are 255.255, and the third octet has 4 bits set (11110000) = 240.

Interconnecting Cisco Networking Devices Part 1 (ICND1) 100-105

The ICND1 (100-105) exam, associated with the Cisco CCENT certification, tests foundational knowledge of network fundamentals, LAN switching, routing, infrastructure services, and infrastructure maintenance. The exam has been retired by Cisco and replaced by the consolidated CCNA 200-301.

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90 min

Time Limit

83%

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