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Question 81

Which protocol is commonly used to exchange routing information between routers within an enterprise network?

1. BGP
2. OSPF
3. HTTP
4. SNMP

Correct Answer: 2

Explanation

OSPF is a widely used interior gateway protocol for exchanging routing information within enterprise networks. It is a link-state protocol that maintains a topology database and calculates shortest paths using the SPF algorithm. OSPF supports hierarchical area designs, route summarization, authentication, and fast convergence. BGP is primarily used for interdomain routing, while HTTP and SNMP serve application and network-management purposes. OSPF is particularly suitable for organizations that require scalable dynamic routing and predictable path selection across multiple network segments.

Question 82

Which Cisco feature can automatically disable a port when an unexpected BPDU is received on an access port?

1. Root Guard
2. BPDU Guard
3. DHCP Snooping
4. Port Security

Correct Answer: 2

Explanation

BPDU Guard protects access ports by placing a port into an error-disabled state when an unexpected Bridge Protocol Data Unit is received. It is commonly enabled on ports configured with PortFast because end-user devices normally should not send spanning-tree BPDUs. If a switch or other Layer 2 device is connected unexpectedly, BPDU Guard can prevent that device from influencing the spanning-tree topology. Root Guard has a different purpose: it prevents a port from becoming an unwanted path toward the spanning-tree root.

Question 83

Which BGP attribute is locally significant and can be used to influence outbound route selection on a Cisco router?

1. Weight
2. MED
3. Origin
4. AS Path

Correct Answer: 1

Explanation

Weight is a Cisco-specific BGP attribute used to influence outbound route selection on an individual router. A higher weight is preferred, and the attribute is locally significant, meaning it is not advertised to other BGP neighbors. This makes weight useful when an administrator wants to select a preferred path on a particular Cisco router without affecting other routers in the autonomous system. Local Preference can influence outbound routing decisions across an autonomous system because it is propagated through iBGP, making it more suitable for network-wide policy.

Question 84

What does an administrative distance of 0 generally indicate?

1. An unknown route
2. A directly connected route
3. A static route
4. An external BGP route

Correct Answer: 2

Explanation

Administrative distance represents the relative trustworthiness of a route source when multiple routing protocols provide routes to the same destination. Directly connected routes generally have an administrative distance of 0, making them the most trusted route source. Static routes commonly have an administrative distance of 1, while different dynamic protocols have their own values. Administrative distance is different from a routing protocol’s metric. The router first considers the most specific prefix and then uses administrative distance and metrics as appropriate when selecting among competing routes.

Question 85

Which protocol is used to provide automatic IP configuration information to IPv4 clients?

1. DHCP
2. DNS
3. NTP
4. LDAP

Correct Answer: 1

Explanation

Dynamic Host Configuration Protocol (DHCP) automatically provides IPv4 clients with network configuration information. A DHCP server can assign an IP address, subnet mask, default gateway, DNS server addresses, lease duration, and other options. The normal DHCP process includes Discover, Offer, Request, and Acknowledgment messages. DHCP reduces administrative effort and prevents many manual addressing errors. When the DHCP server is located on another subnet, a DHCP relay agent can forward client requests across the Layer 3 boundary so clients can still obtain their configuration.

Question 86

Which OSPF network type is commonly used on Ethernet segments?

1. Point-to-point
2. Broadcast
3. Loopback
4. Non-broadcast

Correct Answer: 2

Explanation

Ethernet interfaces commonly operate as OSPF broadcast network types. On a broadcast network, OSPF can use multicast communication to discover neighbors and elect a Designated Router (DR) and Backup Designated Router (BDR). The DR and BDR help reduce the number of full adjacencies required on multiaccess networks. Point-to-point network types are typically associated with direct point-to-point links, while non-broadcast types may be used on technologies where multicast behavior is unavailable. Understanding OSPF network types is important when troubleshooting adjacency and route-exchange issues.

Question 87

Which mechanism can summarize multiple contiguous IPv4 networks into a single route?

1. Route summarization
2. Port security
3. Load balancing
4. NAT overload

Correct Answer: 1

Explanation

Route summarization combines multiple contiguous networks into a single summarized prefix. This reduces the size of routing tables and can decrease the amount of routing information exchanged between network devices. Summarization can also improve stability because changes within the summarized networks may not need to be advertised individually beyond the summary boundary. However, the summary must be designed carefully to avoid routing black holes or inaccurate reachability information. Route summarization can be used with various routing protocols and is especially valuable in large hierarchical network designs.

Question 88

Which protocol provides gateway redundancy using a virtual IP address and an active/standby model on Cisco devices?

1. HSRP
2. OSPF
3. LACP
4. CDP

Correct Answer: 1

Explanation

HSRP provides first-hop redundancy by allowing multiple routers to share a virtual IP address. One router becomes active and forwards traffic, while another router remains in standby and can take over if the active router fails. End devices use the virtual address as their default gateway, so they can continue communicating without changing their configuration. HSRP is particularly useful for improving default-gateway availability in enterprise networks. It is different from OSPF, which exchanges routing information, and LACP, which aggregates physical links.

Question 89

Which protocol is used by Cisco devices to exchange information about directly connected neighbors?

1. LLDP
2. CDP
3. RADIUS
4. BGP

Correct Answer: 2

Explanation

Cisco Discovery Protocol (CDP) is a Cisco proprietary protocol that allows Cisco devices to discover information about directly connected Cisco neighbors. Administrators can use CDP to identify neighboring device names, platforms, interfaces, and other information. It is particularly useful for troubleshooting physical topology and verifying connections. LLDP provides similar discovery capabilities through an industry-standard protocol and supports multivendor environments. Because CDP can expose network information, administrators should evaluate whether it should be enabled on interfaces based on security requirements and network design.

Question 90

Which command displays the MAC address table on a Cisco switch?

1. show ip route
2. show mac address-table
3. show spanning-tree
4. show interfaces status

Correct Answer: 2

Explanation

The show mac address-table command displays the switch’s learned MAC address table. The output can show MAC addresses, associated VLANs, entry types, and the interfaces through which addresses were learned. This command is useful when troubleshooting Layer 2 forwarding, identifying where a device is connected, or investigating unexpected MAC address movement. The routing-table command provides Layer 3 route information, while spanning-tree commands show STP details. Interface status commands provide link information but do not replace the MAC address table.

Question 91

Which BGP attribute is generally preferred when it has a higher value?

1. MED
2. Local Preference
3. Origin
4. AS Path length

Correct Answer: 2

Explanation

BGP Local Preference is generally preferred when it has a higher value. It is used within an autonomous system to influence outbound traffic paths and is propagated through iBGP. For example, an organization can assign a higher local preference to routes learned through a preferred Internet connection. This allows multiple routers to consistently select the desired exit path. MED is generally preferred when lower, while shorter AS Path and lower origin values can also influence route selection depending on the BGP decision process. Policy design should consider the complete BGP topology.

Question 92

Which technology allows network devices to use a centralized controller for policy and automation?

1. SDN
2. STP
3. ARP
4. NAT

Correct Answer: 1

Explanation

Software-Defined Networking (SDN) enables centralized network control and programmability through controllers and software interfaces. Instead of configuring every device independently, administrators can use centralized policies and automation mechanisms to manage network behavior. SDN can improve consistency, simplify operations, and provide programmable control over large network environments. The exact implementation varies between platforms, but centralized control and programmable interfaces are common characteristics. STP handles Layer 2 loop prevention, ARP maps IPv4 addresses to MAC addresses, and NAT performs address translation.

Question 93

What is the primary purpose of DHCP relay?

1. Forward DHCP requests across Layer 3 boundaries
2. Encrypt DHCP messages
3. Replace DNS servers
4. Prevent routing loops

Correct Answer: 1

Explanation

DHCP relay allows DHCP client requests to reach a DHCP server located on a different IP subnet. Because DHCP clients initially use broadcasts, routers normally do not forward these broadcasts between subnets. A relay agent receives the request and forwards it toward the configured DHCP server, allowing centralized DHCP services to support multiple network segments. This avoids the need to deploy a separate DHCP server on every subnet. DHCP relay is therefore especially useful in enterprise networks with many VLANs and centralized network services.

Question 94

Which routing protocol uses DUAL to calculate loop-free paths?

1. OSPF
2. BGP
3. EIGRP
4. RIP

Correct Answer: 3

Explanation

Enhanced Interior Gateway Routing Protocol (EIGRP) uses the Diffusing Update Algorithm (DUAL) to calculate loop-free paths and provide efficient convergence. DUAL allows EIGRP to identify feasible successors and maintain backup paths when appropriate, reducing the need for complete route recalculation after certain topology changes. EIGRP uses a composite metric primarily based on bandwidth and delay by default. OSPF uses SPF, BGP uses a path-selection process based on attributes, and RIP uses hop count. DUAL is therefore a defining feature of EIGRP operation.

Question 95

Which IPv6 address type is used to communicate with multiple receivers simultaneously?

1. Anycast
2. Multicast
3. Unicast
4. Loopback

Correct Answer: 2

Explanation

IPv6 multicast addresses identify groups of interfaces, allowing one packet to be delivered to multiple interested receivers. IPv6 relies heavily on multicast and does not use broadcast in the same manner as IPv4. Multicast is used by several IPv6 functions, including Neighbor Discovery. Anycast addresses identify multiple interfaces but deliver traffic to the nearest appropriate destination according to routing. Unicast communication targets a single interface, while the loopback address is used by a device to communicate with itself. Understanding IPv6 address types is essential for troubleshooting and design.

Question 96

Which security feature can help prevent a host from using an unauthorized IP address on a switch port?

1. IP Source Guard
2. HSRP
3. EtherChannel
4. CDP

Correct Answer: 1

Explanation

IP Source Guard helps prevent unauthorized IP address usage on switch ports by validating source IP information against trusted bindings. It is commonly deployed with DHCP snooping, which provides the binding information used for validation. If traffic arrives with a source IP address that does not match the permitted binding, the switch can block it according to the configured policy. This helps reduce risks such as IP address spoofing. HSRP, EtherChannel, and CDP perform different functions and do not provide this source-address validation capability.

Question 97

Which protocol is commonly used to exchange information between a network management system and managed devices?

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

Correct Answer: 1

Explanation

SNMP is widely used for monitoring and managing network devices. A network management system can query SNMP-enabled devices for operational information such as interface status, traffic counters, CPU utilization, memory usage, and other metrics. Devices can also send notifications called traps or informs when configured events occur. SNMPv3 adds authentication and privacy features that improve security compared with earlier versions. SNMP is therefore an important protocol for network monitoring and operational visibility, although modern environments may also use APIs and streaming telemetry.

Question 98

Which feature allows multiple equal-cost routes to be installed in a routing table?

1. ECMP
2. PAT
3. VRF
4. DHCP snooping

Correct Answer: 1

Explanation

Equal-Cost Multipath (ECMP) allows a router to use multiple paths to the same destination when those paths have equal routing cost. Depending on the platform and configuration, traffic can be distributed across available paths using mechanisms designed to maintain efficient forwarding and avoid packet reordering. ECMP can improve network utilization and provide redundancy without requiring a single path to carry all traffic. It is commonly used in routed data center and enterprise environments. PAT, VRF, and DHCP snooping provide address translation, routing separation, and security functions respectively.

Question 99

Which protocol is commonly used for secure device configuration using REST-style APIs?

1. RESTCONF
2. FTP
3. TFTP
4. CDP

Correct Answer: 1

Explanation

RESTCONF provides a REST-like interface for accessing and manipulating network device configuration and operational data. It commonly uses HTTP or HTTPS and works with structured data models such as YANG. RESTCONF allows automation applications to interact with network devices using familiar web-based methods and data formats such as JSON or XML. HTTPS should be used when secure communication is required. RESTCONF is different from traditional file-transfer protocols because its primary purpose is programmatic management of configuration and operational state rather than simply transferring files.

Question 100

A network engineer wants to identify the next-hop router for a specific destination. Which information should be examined first?

1. ARP cache only
2. MAC address table only
3. Routing table
4. DNS database

Correct Answer: 3

Explanation

The routing table should be examined first to determine how the router will forward traffic toward a specific destination. The routing table identifies the best matching route, next-hop address when applicable, and outgoing interface. After the routing decision is made, the device may use ARP or another Layer 2 resolution mechanism to determine the next-hop MAC address. The MAC address table is used for Layer 2 forwarding, while DNS resolves names rather than selecting network paths. Examining the routing table is therefore the correct first step when troubleshooting Layer 3 forwarding.