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Question 121

Which protocol allows a router to automatically learn IPv6 routes from neighboring routers?

1. DHCPv6
2. OSPFv3
3. ARP
4. SNMP

Correct Answer: 2

Explanation

OSPFv3 is an interior gateway protocol designed to support IPv6 routing. It allows IPv6 routers within an autonomous system to dynamically exchange routing information and calculate optimal paths using the Shortest Path First algorithm. OSPFv3 maintains neighbor relationships and link-state databases similar to OSPF for IPv4, although its operation is adapted for IPv6. DHCPv6 provides host configuration, ARP is not used by IPv6, and SNMP is primarily a network-management protocol. OSPFv3 is therefore an appropriate choice for dynamic IPv6 routing.

Question 122

What is the primary purpose of a default gateway for an end host?

1. To resolve DNS names
2. To provide DHCP services
3. To forward traffic destined for remote networks
4. To assign MAC addresses

Correct Answer: 3

Explanation

A default gateway provides an end host with a Layer 3 path to destinations outside its local subnet. When a host determines that the destination IP address belongs to another network, it sends the packet to its configured default gateway. The gateway then performs routing and forwards the packet toward the destination. Without a properly configured default gateway, a host may still communicate with devices on its local subnet but generally cannot reach remote networks. DNS, DHCP, and MAC-address functions are separate networking services.

Question 123

Which BGP attribute is typically used to influence outbound traffic within an autonomous system?

1. Local Preference
2. MED
3. Origin
4. Community

Correct Answer: 1

Explanation

BGP Local Preference is commonly used to influence outbound traffic within an autonomous system. A higher Local Preference value is normally preferred, allowing administrators to identify which external exit path should be selected by internal BGP routers. Because Local Preference is propagated through iBGP, it can influence routing decisions across the autonomous system rather than only on one router. MED is generally used to influence how external neighbors enter an autonomous system. Local Preference is therefore particularly useful for controlling outbound path selection.

Question 124

Which command displays detailed information about interfaces, including errors, counters, and operational status?

1. show vlan brief
2. show ip route
3. show interfaces
4. show version

Correct Answer: 3

Explanation

The show interfaces command provides detailed information about network interfaces on Cisco devices. The output can include administrative and operational status, bandwidth, duplex settings, packet counters, errors, collisions, input and output statistics, and other useful information. This makes the command valuable when troubleshooting connectivity, performance, and physical-layer problems. show vlan brief focuses on VLAN membership, show ip route displays routing information, and show version provides software and hardware details. Interface statistics can help identify issues such as CRC errors or excessive packet drops.

Question 125

Which security mechanism prevents a switch port from accepting frames with unauthorized source MAC addresses?

1. DHCP relay
2. Port security
3. OSPF authentication
4. NetFlow

Correct Answer: 2

Explanation

Port security restricts which source MAC addresses are allowed on a switch port. Administrators can configure a maximum number of secure MAC addresses and specify how the switch should respond when a violation occurs. Depending on the configured violation mode, unauthorized frames may be dropped and the event may be logged or the port may be placed into an error-disabled state. Port security is commonly used on access ports to reduce unauthorized device connections. It operates at Layer 2 and is different from IP-based security mechanisms.

Question 126

Which protocol is commonly used to provide secure remote CLI access to a Cisco network device?

1. Telnet
2. FTP
3. SSH
4. TFTP

Correct Answer: 3

Explanation

Secure Shell (SSH) provides encrypted remote command-line access to Cisco network devices. It protects administrator credentials and management traffic from being transmitted in clear text across the network. SSH is preferred over Telnet because Telnet does not provide encryption and can expose sensitive information to attackers who can capture network traffic. Cisco devices must be appropriately configured with hostname, domain information, cryptographic keys, user credentials, and VTY settings for SSH access. Secure management protocols are an important part of protecting network infrastructure.

Question 127

Which OSPF router is responsible for reducing the number of adjacencies on a broadcast network?

1. DR
2. ABR
3. ASBR
4. BDR

Correct Answer: 1

Explanation

The Designated Router (DR) reduces the number of OSPF adjacencies required on a multiaccess broadcast network such as Ethernet. Instead of every OSPF router forming a full adjacency with every other router, routers communicate their link-state information through the DR and Backup Designated Router. This reduces unnecessary adjacency relationships and helps control OSPF database synchronization traffic. The BDR provides redundancy if the DR fails. An ABR connects OSPF areas, while an ASBR introduces external routing information into OSPF.

Question 128

Which technology provides logical separation of Layer 2 traffic by assigning devices to different broadcast domains?

1. VRF
2. VLAN
3. NAT
4. GRE

Correct Answer: 2

Explanation

VLANs provide logical Layer 2 segmentation by dividing a switched network into separate broadcast domains. Devices in different VLANs cannot normally communicate directly at Layer 2 and require routing for inter-VLAN communication. VLANs allow organizations to separate users, departments, services, or security zones without requiring physically separate switches for every group. VLAN IDs identify the logical networks, while trunk links can transport traffic belonging to multiple VLANs. VRFs provide Layer 3 routing separation, while NAT translates addresses and GRE provides tunneling.

Question 129

Which protocol is designed to automatically detect and negotiate network parameters between two Ethernet devices?

1. LACP
2. CDP
3. LLDP
4. Auto-negotiation

Correct Answer: 4

Explanation

Ethernet auto-negotiation allows connected interfaces to negotiate capabilities such as speed and duplex settings when supported by both devices. This helps interfaces establish compatible operational parameters without requiring every setting to be manually configured. Proper speed and duplex negotiation is important for reliable Ethernet communication. LACP negotiates link aggregation, while CDP and LLDP exchange information about neighboring devices. If auto-negotiation is disabled or configured inconsistently, speed or duplex mismatches can occur and may lead to poor performance, packet errors, or connectivity problems.

Question 130

Which BGP feature allows multiple routes to be represented by a single summarized prefix?

1. Route reflector
2. Route aggregation
3. Community tagging
4. Next-hop modification

Correct Answer: 2

Explanation

BGP route aggregation allows multiple more-specific prefixes to be represented by a summarized route. For example, several contiguous networks can potentially be advertised as one larger prefix, reducing routing-table size and the amount of routing information exchanged. Aggregation can improve scalability, but administrators must carefully consider reachability and potential traffic black holes. BGP supports several methods for controlling how aggregate routes are advertised and what attributes they carry. Route reflectors solve a different problem by reducing the need for full-mesh iBGP sessions.

Question 131

Which service translates private IPv4 addresses into a public address for Internet communication?

1. NAT
2. OSPF
3. STP
4. NTP

Correct Answer: 1

Explanation

Network Address Translation (NAT) translates IP addresses between different addressing domains. A common enterprise use is translating private IPv4 addresses into publicly routable addresses so internal hosts can communicate with the Internet. NAT can operate in several forms, including static NAT, dynamic NAT, and Port Address Translation (PAT). PAT allows many internal hosts to share a smaller number of public IPv4 addresses by using different Layer 4 port numbers. NAT helps conserve public IPv4 addresses and can also provide a degree of address-space separation.

Question 132

Which mechanism can prevent unauthorized DHCP servers from responding to client requests?

1. PortFast
2. Root Guard
3. DHCP snooping
4. IP SLA

Correct Answer: 3

Explanation

DHCP snooping helps protect a switched network from unauthorized or rogue DHCP servers. Interfaces can be classified as trusted or untrusted. DHCP server responses are normally permitted only through trusted interfaces, while untrusted access ports are prevented from sending unauthorized DHCP server messages. DHCP snooping also creates bindings between IP addresses, MAC addresses, VLANs, and interfaces, which can support security features such as Dynamic ARP Inspection and IP Source Guard. This makes DHCP snooping an important Layer 2 security mechanism in enterprise networks.

Question 133

Which protocol is used to prevent Layer 2 switching loops by placing redundant paths into a blocking state?

1. STP
2. BGP
3. OSPF
4. DHCP

Correct Answer: 1

Explanation

Spanning Tree Protocol (STP) prevents Layer 2 switching loops by calculating a loop-free logical topology. When redundant physical paths exist between switches, STP can place selected interfaces into a non-forwarding state while maintaining them as potential backup paths. If the active topology changes, a previously blocked path may become available. Without STP or another loop-prevention mechanism, Layer 2 loops can cause broadcast storms, duplicate frames, and MAC-table instability. STP therefore provides an essential protection mechanism in redundant switched Ethernet networks.

Question 134

Which Cisco technology can monitor traffic statistics by exporting flow information to a collector?

1. SPAN
2. NetFlow
3. CDP
4. VTP

Correct Answer: 2

Explanation

NetFlow provides visibility into network traffic by collecting information about IP flows and exporting flow records to a monitoring or analysis system. Flow records can contain information such as source and destination addresses, ports, protocols, interfaces, and packet or byte counts. This information helps administrators understand traffic patterns, identify high-volume applications, investigate anomalies, and support capacity planning. NetFlow does not normally capture the complete contents of every packet. It focuses on metadata describing traffic flows, making it useful for network assurance and operational analysis.

Question 135

Which IPv6 address is used for communication with all nodes on the local link?

1. FF02::1
2. FF02::2
3. FE80::1
4. 2001:DB8::1

Correct Answer: 1

Explanation

FF02::1 is the IPv6 link-local multicast address for all nodes on the local link. IPv6 multicast addresses begin with FF, and the scope information determines where the multicast traffic is valid. FF02 indicates link-local scope, meaning the traffic remains on the local network segment. FF02::2 represents all IPv6 routers on the local link. FE80::/10 is the IPv6 link-local unicast range, while 2001:DB8::/32 is reserved for documentation examples. These multicast groups are important to IPv6 neighbor and router discovery.

Question 136

Which technology can mirror traffic from one switch interface to another for packet analysis?

1. HSRP
2. SPAN
3. VRRP
4. LACP

Correct Answer: 2

Explanation

Switched Port Analyzer (SPAN), also called port mirroring, copies traffic from selected source interfaces or VLANs to a destination interface where a monitoring or packet-analysis device is connected. Network engineers can use SPAN to inspect packets, troubleshoot connectivity, investigate suspicious traffic, and analyze application behavior. SPAN does not normally alter the original traffic; it provides a copy for observation. HSRP and VRRP provide gateway redundancy, while LACP creates link aggregation. SPAN is therefore primarily a network visibility and troubleshooting feature.

Question 137

Which protocol provides a standard method for discovering neighboring network devices from different vendors?

1. CDP
2. LLDP
3. VTP
4. DTP

Correct Answer: 2

Explanation

Link Layer Discovery Protocol (LLDP) is an IEEE-standard protocol that allows network devices to advertise and learn information about directly connected neighbors. Because LLDP is vendor-neutral, it is useful in multivendor environments where devices from different manufacturers need to exchange basic topology information. Administrators can use LLDP to identify neighboring device names, ports, capabilities, and other details. CDP provides similar functionality but is Cisco proprietary. VTP manages VLAN information in supported environments, while DTP negotiates trunking on Cisco switches.

Question 138

Which QoS technique temporarily stores packets in memory so they can be transmitted later at a controlled rate?

1. Classification
2. Policing
3. Shaping
4. Marking

Correct Answer: 3

Explanation

Traffic shaping controls the transmission rate by buffering excess traffic and sending it later according to a configured rate. This can smooth traffic bursts and help match the transmission rate to the available bandwidth of a downstream connection. Unlike policing, which can discard or remark traffic that exceeds a configured rate, shaping generally uses buffering to delay packets. Classification identifies traffic classes, while marking assigns QoS values to packets. Traffic shaping is particularly useful on interfaces where controlling bursts and maintaining a predictable traffic rate is important.

Question 139

Which automation technology uses YAML-based playbooks to describe configuration and operational tasks?

1. Ansible
2. NETCONF
3. RESTCONF
4. SNMP

Correct Answer: 1

Explanation

Ansible is an automation platform that commonly uses YAML-based playbooks to describe tasks that should be performed on managed systems. Network administrators can use Ansible to automate configuration changes, gather operational information, validate device states, and perform repeatable workflows across many devices. Automation reduces repetitive manual work and can improve consistency when properly designed. NETCONF and RESTCONF are management protocols, while SNMP is primarily used for monitoring and management information exchange. Ansible can use network-specific modules and protocols to communicate with Cisco infrastructure.

Question 140

Which Cisco IOS feature can generate an ICMP echo request from a router to test reachability to a remote destination at scheduled intervals?

1. SPAN
2. IP SLA
3. DHCP relay
4. VTP

Correct Answer: 2

Explanation

Cisco IP Service Level Agreements (IP SLA) can actively generate test traffic, such as ICMP echo requests, to measure reachability and performance between network devices. An IP SLA operation can monitor metrics such as response time, delay, jitter, or packet loss depending on the configured probe type. Results can be used for troubleshooting, performance monitoring, and dynamic network decisions when combined with other Cisco features. IP SLA is therefore useful for proactively detecting connectivity or service-quality problems before users report them.