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Question 141

Which BGP message is used to maintain an established BGP session when no other messages are being exchanged?

1. UPDATE
2. KEEPALIVE
3. NOTIFICATION
4. OPEN

Correct Answer: 2

Explanation

BGP KEEPALIVE messages maintain an established BGP session when no other BGP messages are being exchanged. They are sent periodically between BGP peers to confirm that the session remains operational. If a router stops receiving expected KEEPALIVE or other BGP messages within the configured hold time, it can consider the neighbor unavailable and terminate the session. OPEN messages establish the session, UPDATE messages exchange routing information, and NOTIFICATION messages report errors and terminate the session when necessary.

Question 142

Which protocol is primarily responsible for mapping an IPv4 address to a MAC address on a local network?

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

Correct Answer: 3

Explanation

Address Resolution Protocol (ARP) maps an IPv4 address to a corresponding MAC address on a local network segment. When a host needs to send an IPv4 packet to another device on the same subnet, it can use an ARP request to discover the destination’s MAC address. The device owning that IP address responds with an ARP reply containing its MAC address. The sender can then encapsulate the IP packet in an Ethernet frame. ARP is a Layer 2/Layer 3 interaction used specifically with IPv4.

Question 143

Which OSPF component contains information about the topology of an OSPF area?

1. Routing table
2. ARP cache
3. LSDB
4. MAC address table

Correct Answer: 3

Explanation

The OSPF Link-State Database (LSDB) contains information describing the topology of an OSPF area. Routers within the same area maintain synchronized LSDB information by exchanging Link-State Advertisements. OSPF then uses the information in the LSDB to run the Shortest Path First algorithm and calculate routes. The resulting best routes are installed in the routing table. The ARP cache stores IPv4-to-MAC mappings, while the MAC address table is used by switches for Layer 2 forwarding. The LSDB is therefore central to OSPF’s link-state operation.

Question 144

Which command displays the OSPF neighbors discovered by a Cisco router?

1. show ip ospf neighbor
2. show ip route
3. show interfaces
4. show vlan brief

Correct Answer: 1

Explanation

The show ip ospf neighbor command displays information about OSPF neighbor relationships. The output can include the neighbor router ID, priority, state, dead timer, and local interface. This command is particularly useful when troubleshooting OSPF adjacency problems. Administrators can determine whether a neighbor has reached a full adjacency state or is stuck in another state. If an expected neighbor does not appear, engineers can investigate interface configuration, network type, area settings, timers, authentication, and connectivity. The command provides a quick view of OSPF neighbor status.

Question 145

Which IPv4 address range is reserved for private Class A addressing?

1. 172.16.0.0/12
2. 192.168.0.0/16
3. 169.254.0.0/16
4. 10.0.0.0/8

Correct Answer: 4

Explanation

The IPv4 range 10.0.0.0/8 is reserved for private addressing and provides a large private address space. Addresses in this range are not directly routable across the public Internet and are commonly used within enterprise networks. The other major private IPv4 ranges are 172.16.0.0/12 and 192.168.0.0/16. Private addresses are frequently combined with NAT or PAT when internal devices need to communicate with public Internet destinations. Using private addressing helps organizations conserve limited public IPv4 address space.

Question 146

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

1. Local Preference
2. MED
3. Weight
4. Router ID

Correct Answer: 2

Explanation

Multi-Exit Discriminator (MED) is a BGP attribute that can influence how an external autonomous system selects an entry point into another autonomous system. When comparing routes from the same neighboring autonomous system, a lower MED is generally preferred. MED is commonly used when an organization has multiple connections to another autonomous system and wants to indicate a preferred inbound path. Local Preference and Weight are generally preferred when higher, while Router ID is used in later BGP decision steps rather than as a traffic-engineering metric.

Question 147

Which security technology dynamically validates ARP packets using trusted DHCP snooping bindings?

1. IP Source Guard
2. Dynamic ARP Inspection
3. PortFast
4. Root Guard

Correct Answer: 2

Explanation

Dynamic ARP Inspection (DAI) helps protect a switched network against ARP spoofing and poisoning attacks. It can validate ARP packets against trusted IP-to-MAC bindings learned through DHCP snooping. If an ARP packet does not match the expected binding information, the switch can discard it. This helps prevent attackers from impersonating another device or gateway by sending forged ARP information. IP Source Guard validates source IP information, while PortFast and Root Guard protect spanning-tree behavior. DAI is therefore specifically focused on validating ARP traffic.

Question 148

Which protocol provides centralized authentication and authorization for network administrators while supporting command-level authorization?

1. DHCP
2. RADIUS
3. TACACS+
4. DNS

Correct Answer: 3

Explanation

TACACS+ is commonly used for centralized administrative access to network devices and supports separate authentication, authorization, and accounting functions. One important capability is granular authorization, which can allow administrators to be restricted to specific commands or privilege levels. This makes TACACS+ useful in environments where organizations need detailed control over network-device administration. RADIUS is also widely used for AAA, especially for network access, but TACACS+ is traditionally associated with centralized device administration and detailed command authorization.

Question 149

Which protocol is used to dynamically distribute VLAN information between supported Cisco switches?

1. VTP
2. STP
3. LACP
4. HSRP

Correct Answer: 1

Explanation

VLAN Trunking Protocol (VTP) can distribute VLAN configuration information between supported Cisco switches within a VTP domain. It can simplify VLAN management by allowing VLAN additions, deletions, and modifications to be propagated from a VTP server to other participating switches. However, VTP must be configured carefully because an incorrect configuration can affect VLAN information across multiple switches. STP prevents Layer 2 loops, LACP negotiates link aggregation, and HSRP provides first-hop redundancy. VTP is specifically associated with VLAN database distribution.

Question 150

Which routing method uses the most specific matching network prefix when forwarding an IP packet?

1. Administrative distance
2. Longest prefix match
3. Round-robin selection
4. Default gateway selection

Correct Answer: 2

Explanation

Longest prefix match means a router selects the routing-table entry with the most specific prefix that matches the destination IP address. For example, if a destination matches both a /16 and a /24 route, the /24 route is more specific and is selected. This principle allows routing tables to contain broad summary routes while still providing more specific paths for particular networks. Administrative distance helps choose between routing sources when appropriate, but the router first considers the most specific matching prefix when determining how to forward traffic.

Question 151

Which wireless architecture commonly centralizes management of lightweight access points?

1. Autonomous routing architecture
2. Controller-based WLAN architecture
3. Peer-to-peer routing
4. Static VLAN architecture

Correct Answer: 2

Explanation

A controller-based WLAN architecture centralizes management and control of lightweight wireless access points through a Wireless LAN Controller (WLC). The controller can provide functions such as configuration management, security policies, RF management, roaming support, and centralized monitoring. This architecture simplifies administration when many access points are deployed across an enterprise. Autonomous access points can operate independently, but controller-based designs provide centralized coordination and policy enforcement. The appropriate architecture depends on organizational requirements, scale, operational model, and the wireless platform being deployed.

Question 152

Which protocol is used to transfer files between network devices without providing encryption?

1. SSH
2. SCP
3. TFTP
4. HTTPS

Correct Answer: 3

Explanation

Trivial File Transfer Protocol (TFTP) is a simple file-transfer protocol commonly used in network environments for tasks such as transferring configuration files, IOS images, or boot files. TFTP does not provide encryption or strong authentication, so it should be used only in controlled and trusted environments. SCP provides secure file transfer through SSH, while HTTPS provides encrypted web communication. TFTP’s simplicity makes it useful for certain network-management tasks, but its lack of security features makes it unsuitable for transferring sensitive information across untrusted networks.

Question 153

Which protocol is used by BGP peers to establish a TCP connection?

1. TCP
2. UDP
3. ICMP
4. GRE

Correct Answer: 1

Explanation

BGP uses TCP as its transport protocol and establishes peer sessions using TCP port 179. TCP provides reliable, connection-oriented delivery for BGP messages, allowing routing updates and session-management information to be exchanged reliably. BGP does not require a separate transport mechanism for retransmitting lost messages because TCP handles reliability. UDP is commonly used by protocols such as DNS queries and DHCP, while ICMP supports diagnostic and control functions. GRE provides tunneling rather than serving as BGP’s standard transport protocol.

Question 154

Which network service automatically resolves a hostname such as router.example.com into an IP address?

1. NTP
2. DNS
3. SNMP
4. Syslog

Correct Answer: 2

Explanation

Domain Name System (DNS) resolves human-readable hostnames into IP addresses and can also provide other name-related information. When a network device or client needs to communicate with a host identified by a domain name, it can query a DNS server to obtain the corresponding address. DNS eliminates the need for users and applications to remember numerical IP addresses for every service. NTP synchronizes clocks, SNMP provides management information, and Syslog transports event messages. DNS is therefore the service responsible for hostname resolution.

Question 155

Which IPv6 address type identifies a group of interfaces and delivers traffic to all members of that group?

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

Correct Answer: 3

Explanation

IPv6 multicast addresses identify a group of interfaces, allowing packets to be delivered to multiple participating receivers. IPv6 uses multicast extensively for functions such as Neighbor Discovery and router discovery. Unlike IPv4, IPv6 does not rely on broadcast as a general communication method. Anycast addresses can be assigned to multiple interfaces but traffic is normally delivered to the nearest appropriate interface according to routing. Unicast identifies a single destination, while the IPv6 loopback address is used for communication within the local host.

Question 156

Which technology can provide multiple virtual networks over a shared Layer 3 IP transport network by using VXLAN tunnels?

1. GRE
2. VXLAN
3. STP
4. HSRP

Correct Answer: 2

Explanation

VXLAN creates Layer 2 overlay networks across a Layer 3 IP underlay by encapsulating Ethernet frames inside UDP packets. This allows network segments to extend across routed infrastructure while maintaining logical separation. VXLAN uses a 24-bit VXLAN Network Identifier (VNI), providing a much larger segmentation space than traditional 12-bit VLAN IDs. VXLAN is widely associated with modern data center designs and can work with control-plane technologies such as BGP EVPN. STP and HSRP serve different functions and do not provide this overlay-network capability.

Question 157

Which BGP component prevents the need for a full mesh of iBGP sessions within an autonomous system?

1. Route reflector
2. ASBR
3. DR
4. Stub router

Correct Answer: 1

Explanation

A BGP route reflector reduces the need for a full mesh of internal BGP sessions. In a traditional iBGP design, routers generally need direct iBGP sessions with one another because routes learned from one iBGP neighbor are not normally advertised to another iBGP neighbor. A route reflector can receive routes from clients and reflect them to other clients, simplifying the topology. This improves scalability in larger autonomous systems. Route reflectors should be designed carefully to avoid routing inconsistencies and unnecessary path-selection complications.

Question 158

Which protocol is commonly used to securely retrieve structured network configuration and operational data using an SSH-based management session?

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

Correct Answer: 1

Explanation

NETCONF is a network-management protocol designed for retrieving and modifying configuration and operational data. It commonly operates over SSH and works with structured data models, particularly YANG. NETCONF supports operations such as retrieving configuration, editing configuration, validating changes, and committing updates depending on the implementation. Its structured approach makes it useful for network automation and transactional configuration management. Telnet, TFTP, and FTP do not provide the same model-driven network configuration capabilities. NETCONF is therefore an important protocol in programmable Cisco network environments.

Question 159

Which high-availability protocol uses a virtual IP address shared by a group of routers and is an open standard?

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

Correct Answer: 3

Explanation

Virtual Router Redundancy Protocol (VRRP) is an open-standard first-hop redundancy protocol. Multiple routers participate in a virtual router group and share a virtual IP address that can be configured as the default gateway for hosts. One router acts as the master while another can take over if the master becomes unavailable. VRRP improves gateway availability without requiring hosts to change their default-gateway configuration. HSRP and GLBP are Cisco technologies with different operational characteristics, while LACP is used for link aggregation rather than gateway redundancy.

Question 160

Which data modeling language is commonly used with NETCONF and RESTCONF to describe network configuration and operational data?

1. JSON
2. XML
3. YANG
4. YAML

Correct Answer: 3

Explanation

YANG is a data modeling language used to define the structure, constraints, and relationships of configuration and operational data in network-management systems. NETCONF and RESTCONF commonly use YANG models to provide a structured representation of network resources. This model-driven approach allows automation systems to interact with devices in a consistent and predictable manner. JSON and XML can represent data, while YAML is commonly used for configuration files and automation tools, but YANG specifically defines the underlying network data model used by these management protocols.