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

Question 1: Which command verifies the OSPF neighbor state on a Cisco router?

show ospf database
show ip ospf neighbor (Correct answer)
show ip protocols
show ip route ospf

Correct answer: show ip ospf neighbor

The 'show ip ospf neighbor' command displays OSPF neighbor relationships and their current state.

Question 2: Which command verifies that OSPF is enabled on a specific interface and shows its cost?

show ip protocols
show ip route ospf
show ip ospf neighbor detail
show ip ospf interface brief (Correct answer)

Correct answer: show ip ospf interface brief

'show ip ospf interface brief' lists all OSPF-enabled interfaces with their area, IP, cost, state, and neighbor counts.

Question 3: In the OSI model, which layer handles the conversion of data formats such as encryption and compression?

Presentation (Correct answer)
Transport
Session
Application

Correct answer: Presentation

The Presentation layer (Layer 6) translates data formats, handles encryption/decryption, and compression.

Question 4: Which command displays the OSPF neighbor table on a Cisco router?

show ip ospf database
show ip route ospf
show ip ospf interface
show ip ospf neighbor (Correct answer)

Correct answer: show ip ospf neighbor

'show ip ospf neighbor' displays the neighbor ID, state, dead time, and interface for each OSPF neighbor.

Question 5: A router has two routes to 192.168.10.0/24: one via OSPF with metric 20 and one via RIP with metric 5. Which route is installed in the routing table by default?

OSPF route, because OSPF has a lower AD of 110 (Correct answer)
RIP route, because RIP has a lower AD of 120
RIP route, because it has a lower metric
Both routes are installed via load balancing

Correct answer: OSPF route, because OSPF has a lower AD of 110

Administrative Distance is compared before metric; OSPF AD 110 is lower than RIP AD 120, so the OSPF route wins.

Question 6: What is the primary function of a VPN?

To improve network speed.
To provide secure remote access to a private network (Correct answer)
To assign IP addresses dynamically.
To share files over the internet.

Correct answer: To provide secure remote access to a private network

The primary function of a VPN (Virtual Private Network) is to create a secure, encrypted connection over a public network, such as the internet. This allows remote users to access a private network as if they were directly connected, ensuring data confidentiality and integrity. VPNs are crucial for secure remote work and protecting sensitive information from interception.

Question 7: Which command displays the contents of the EIGRP topology table?

show ip route eigrp
show eigrp database
show ip eigrp neighbors
show ip eigrp topology (Correct answer)

Correct answer: show ip eigrp topology

The 'show ip eigrp topology' command shows all EIGRP routes including successors and feasible successors.

Question 8: Which command configures the maximum number of MAC addresses allowed on a port security-enabled interface?

ip port-security maximum-hosts 2
switchport port-security maximum 2 (Correct answer)
port-security max-mac-address 2
switchport security mac-limit 2

Correct answer: switchport port-security maximum 2

The 'switchport port-security maximum' command sets the number of MAC addresses allowed on the interface before a violation occurs.

Question 9: What does the 'show cdp neighbors' command display?

OSPF neighbor adjacency states
Routing table entries for directly connected networks
MAC address table of connected switches
Directly connected Cisco devices and their interface information (Correct answer)

Correct answer: Directly connected Cisco devices and their interface information

CDP (Cisco Discovery Protocol) neighbors shows directly connected Cisco devices, their platform, capabilities, and connected interface.

Question 10: What is the MOST effective way for new ICND1 professionals to build competency in their field?

Studying certification materials exclusively
Focusing solely on the most advanced topics
Combining formal education, mentored practice, and ongoing professional development (Correct answer)
Learning entirely through trial and error

Correct answer: Combining formal education, mentored practice, and ongoing professional development

Building professional competency requires a multi-faceted approach: formal education provides foundational knowledge, mentored practice develops applied skills under guidance, and ongoing professional development ensures continuous growth and currency in the field.

Question 11: What is the purpose of the OSPF dead interval?

The time OSPF waits before electing a new DR
The time after which a neighbor is declared down if no Hello is received (Correct answer)
The interval between LSA flooding cycles
The timeout for database exchange between neighbors

Correct answer: The time after which a neighbor is declared down if no Hello is received

If a router does not receive a Hello from a neighbor within the dead interval, it declares that neighbor down and recalculates routes.

Question 12: Which of the following best describes a classless routing protocol?

It only supports summarization at class boundaries
It does not support VLSM
It includes subnet mask information in routing updates (Correct answer)
It groups routes by class A, B, or C

Correct answer: It includes subnet mask information in routing updates

Classless routing protocols include subnet mask (prefix length) in their updates, allowing support for VLSM and CIDR.

Question 13: What is the function of the configuration register value 0x2142 on a Cisco router?

Enables ROM Monitor mode
Forces a full factory reset
Bypasses the startup configuration in NVRAM (Correct answer)
Boots normally from flash

Correct answer: Bypasses the startup configuration in NVRAM

Config register 0x2142 tells the router to ignore the startup-config, which is used for password recovery procedures.

Question 14: Which command configures a default route on a Cisco router and forwards traffic to next-hop 203.0.113.1?

ip default-route 0.0.0.0 203.0.113.1
ip route 255.255.255.255 255.255.255.255 203.0.113.1
ip route default 203.0.113.1
ip route 0.0.0.0 0.0.0.0 203.0.113.1 (Correct answer)

Correct answer: ip route 0.0.0.0 0.0.0.0 203.0.113.1

A default static route uses the 0.0.0.0 0.0.0.0 network and mask to match all destinations not found in the routing table.

Question 15: Which PDU name is used at the OSI Transport layer?

Bit
Frame
Segment (Correct answer)
Packet

Correct answer: Segment

The Transport layer (Layer 4) encapsulates data into segments.

Question 16: How many usable host addresses are available in a /27 subnet?

62
30 (Correct answer)
14
32

Correct answer: 30

A /27 subnet has 32 total addresses (2^5), minus 2 for network and broadcast, leaving 30 usable hosts.

Question 17: What action does BPDU Guard take when a BPDU is received on a PortFast-enabled port?

It places the port into an err-disabled state (Correct answer)
It logs the event and alerts the network administrator only
It converts the port to a trunk port automatically
It increases the port priority to absorb the BPDU

Correct answer: It places the port into an err-disabled state

BPDU Guard immediately shuts down the port into err-disabled state when a BPDU is detected, protecting the STP topology from unauthorized switches.

Question 18: What does it mean when a neighbor shows 'FULL/DR' in the 'show ip ospf neighbor' output?

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

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 19: Which network address belongs to the same /27 subnet as host 192.168.5.100?

192.168.5.96 (Correct answer)
192.168.5.112
192.168.5.64
192.168.5.128

Correct answer: 192.168.5.96

A /27 has a block size of 32; 96 ≤ 100 < 128, so the network address is 192.168.5.96.

Question 20: What is the recommended best practice for securing unused switch ports?

Shut down the ports and assign them to an unused VLAN (Correct answer)
Enable port security with maximum of 10 MAC addresses
Configure the ports as trunk ports
Apply an extended ACL to each unused port

Correct answer: Shut down the ports and assign them to an unused VLAN

Shutting down unused ports and assigning them to an unused VLAN prevents unauthorized devices from connecting to the network.

Question 21: Which mechanism allows an IPv6 host to automatically generate its interface ID from its 48-bit MAC address?

DHCPv6 stateful
SLAAC with EUI-64 (Correct answer)
6to4 tunneling
IPv6 anycast

Correct answer: SLAAC with EUI-64

EUI-64 inserts FFFE in the middle of the MAC address and flips the universal/local bit to form a 64-bit interface ID used with SLAAC.

Question 22: How many total IP addresses (including network and broadcast) does a /29 subnet contain?

32
16
6
8 (Correct answer)

Correct answer: 8

A /29 has 32 - 29 = 3 host bits, so 2^3 = 8 total addresses.

Question 23: Which attack technique allows a host to send frames on a VLAN it should not access by exploiting trunk negotiation?

STP root takeover
MAC flooding
VLAN hopping via double tagging (Correct answer)
ARP poisoning

Correct answer: VLAN hopping via double tagging

Double-tagging attacks embed an inner VLAN tag that gets processed after the outer tag is stripped at the first trunk.

Question 24: 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 25: Which OSPF network type is assigned by default on a Cisco Ethernet interface?

Broadcast (Correct answer)
Point-to-multipoint
Non-broadcast
Point-to-point

Correct answer: Broadcast

Ethernet interfaces default to the OSPF broadcast network type, which elects a DR and BDR.

Question 26: How many subnets are created when a Class C network is subnetted with a /27 mask?

16
4
8 (Correct answer)
6

Correct answer: 8

A Class C uses a /24 default; borrowing 3 additional bits for subnetting gives 2^3 = 8 subnets.

Question 27: Which NTP stratum level indicates a directly connected reference clock source such as an atomic clock?

Stratum 2
Stratum 16
Stratum 1
Stratum 0 (Correct answer)

Correct answer: Stratum 0

Stratum 0 devices are reference clock sources (atomic clocks, GPS); Stratum 1 servers sync directly to them.

Question 28: Which Cisco IOS command displays the status of all configured Frame Relay PVCs on an interface?

show frame-relay pvc (Correct answer)
show frame-relay map
show frame-relay lmi
show interface serial

Correct answer: show frame-relay pvc

'show frame-relay pvc' displays statistics and status (ACTIVE, INACTIVE, DELETED) for each PVC.

Question 29: What does the 802.1Q tag inserted into an Ethernet frame contain?

VLAN ID and a 3-bit priority field (CoS) (Correct answer)
Source MAC, VLAN ID, and CoS bits
VLAN ID, subnet mask, and frame checksum
Destination IP and VLAN ID only

Correct answer: VLAN ID and a 3-bit priority field (CoS)

The 4-byte 802.1Q tag includes a 12-bit VLAN ID (supporting VLANs 1–4094) and a 3-bit Class of Service (CoS) priority field.

Question 30: A technician runs 'show ip route' and sees a route marked with 'C'. What does the 'C' designation mean?

The route was learned via OSPF
The route is a directly connected network (Correct answer)
The route was learned via RIP
The route is a candidate default route

Correct answer: The route is a directly connected network

The 'C' code in the routing table indicates a directly connected network on an active interface.

Question 31: When assessment results for a Interconnecting Cisco Networking Devices Part 1 evaluation are inconclusive, the BEST practice is to:

Discard the results and start over completely
Delay reporting until results are favorable
Conduct additional assessment using alternative methods (Correct answer)
Report the results as definitive anyway

Correct answer: Conduct additional assessment using alternative methods

Inconclusive results require additional assessment using alternative methods to gather more data. This triangulation approach helps clarify findings without compromising the integrity of the assessment process.

Question 32: Which protocol is used to map an IP address to a MAC address on a local network?

DNS
DHCP
ARP (Correct answer)
RARP

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 33: What is the broadcast address of the subnet 10.0.0.0/8?

10.128.0.0
10.255.255.254
10.0.0.255
10.255.255.255 (Correct answer)

Correct answer: 10.255.255.255

For 10.0.0.0/8, all 24 host bits set to 1 gives a broadcast address of 10.255.255.255.

Question 34: What command enables Syslog messages to be sent to a remote Syslog server at 10.0.0.50?

debug logging 10.0.0.50
logging 10.0.0.50 (Correct answer)
syslog enable 10.0.0.50
log-server 10.0.0.50

Correct answer: logging 10.0.0.50

The 'logging [ip-address]' command in global configuration mode directs Syslog messages to a remote Syslog server.

Question 35: Which WAN technology uses 23 B-channels and 1 D-channel in its PRI (Primary Rate Interface) configuration in North America?

Frame Relay
ISDN (Correct answer)
DSL
ATM

Correct answer: ISDN

ISDN PRI in North America provides 23 bearer (B) channels at 64 Kbps each plus one 64 Kbps delta (D) channel for signaling.

Question 36: What is the subnet mask in dotted-decimal notation for a /20 prefix?

255.255.240.0 (Correct answer)
255.255.252.0
255.255.224.0
255.255.248.0

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.

Question 37: What is the broadcast address of the subnet 192.168.10.64/26?

192.168.10.128
192.168.10.191
192.168.10.126
192.168.10.127 (Correct answer)

Correct answer: 192.168.10.127

A /26 block size is 64; subnet 192.168.10.64 has broadcast at .127 (64+64-1).

Question 38: A host receives a 169.254.x.x address. What does this indicate?

DHCP discovery succeeded but the server is overloaded
The default gateway is unreachable
The host failed to receive a DHCP lease and assigned itself an APIPA address (Correct answer)
The host is configured with a static IP

Correct answer: The host failed to receive a DHCP lease and assigned itself an APIPA address

169.254.0.0/16 is the APIPA (Automatic Private IP Addressing) range used when a DHCP client cannot reach a server.

Question 39: When assessment results for a Interconnecting Cisco Networking Devices Part 1 evaluation are inconclusive, the BEST practice is to:

Report the results as definitive anyway
Delay reporting until results are favorable
Discard the results and start over completely
Conduct additional assessment using alternative methods (Correct answer)

Correct answer: Conduct additional assessment using alternative methods

Question 40: What does a subnet mask do in networking?

It divides the IP address into network and host parts (Correct answer)
It defines the routing table.
It encrypts data in the network.
It prevents unauthorized network access.

Correct answer: It divides the IP address into network and host parts

A subnet mask is a 32-bit number that works in conjunction with an IP address to define the network and host portions of the address. It helps devices determine if a destination IP address is on the same local network or if it needs to be routed to a different network, facilitating efficient data transmission.

Question 41: Which statement about RIPv2 is true?

It does not support authentication
It uses multicast address 224.0.0.9 for updates (Correct answer)
It uses unicast to send routing updates
It supports a maximum hop count of 16

Correct answer: It uses multicast address 224.0.0.9 for updates

RIPv2 sends routing updates to the multicast address 224.0.0.9, unlike RIPv1 which used broadcast.

Question 42: How should a ICND1 professional manager address underperformance within their team?

Ignore it until formal review periods
Provide timely, specific feedback with support and a clear improvement plan (Correct answer)
Immediately reassign the individual to a different role
Publicly address the issue in team meetings

Correct answer: Provide timely, specific feedback with support and a clear improvement plan

Addressing underperformance requires timely intervention with specific, objective feedback about the performance gap. Providing support resources and a clear improvement plan with defined expectations and timelines gives the individual a fair opportunity to improve.

Question 43: How many subnets are created when you borrow 3 bits from the host portion of a Class C address?

16
14
6
8 (Correct answer)

Correct answer: 8

Borrowing 3 bits yields 2^3 = 8 subnets (using the all-zeroes and all-ones subnets per modern practice).

Question 44: What is the most important professional competency for ICND1 certification in ospf configuration?

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

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 45: Which show command confirms that OSPF routes have been installed in the routing table and displays their costs?

show ip ospf topology
show ip ospf database
show ip ospf neighbor
show ip route ospf (Correct answer)

Correct answer: show ip route ospf

'show ip route ospf' displays all OSPF-learned routes with their metric (cost) and next-hop information.

Question 46: Which command on a Cisco router excludes the addresses 192.168.1.1 through 192.168.1.10 from being assigned by DHCP?

ip dhcp excluded-address 192.168.1.1 192.168.1.10 (Correct answer)
ip dhcp reserve 192.168.1.1 192.168.1.10
no ip dhcp address 192.168.1.1 192.168.1.10
ip dhcp pool exclude 192.168.1.1 192.168.1.10

Correct answer: ip dhcp excluded-address 192.168.1.1 192.168.1.10

'ip dhcp excluded-address' prevents the DHCP server from leasing the specified address range to clients.

Question 47: Which of the following is a private IP address?

172.256.256.256
8.8.8.8
192.168.1.1 (Correct answer)
64.233.160.0

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 48: Which Cisco IOS command displays the Layer 2 to Layer 3 address mappings learned by a router?

show ip arp (Correct answer)
show ip route
show mac-address-table
show cdp neighbors detail

Correct answer: show ip arp

'show ip arp' displays the ARP cache, which maps IP addresses to MAC addresses on connected segments.

Question 49: Which file system location stores the Cisco IOS image on most routers?

RAM
Flash (Correct answer)
ROM
NVRAM

Correct answer: Flash

The IOS image is stored in Flash memory, which is non-volatile and retains content after power loss.

Question 50: Which documentation is essential when working with infrastructure maintenance in ICND1?

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

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.

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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