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Question 321

Which protocol uses a reliable transport connection and port 179 for BGP peer communication?

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

Correct Answer: 2

Explanation

BGP uses TCP as its transport protocol and establishes peer sessions through TCP port 179. TCP provides reliable, connection-oriented communication, allowing BGP to exchange routing information without implementing its own packet-retransmission mechanism. Before routing updates are exchanged, BGP peers establish a TCP connection and negotiate session parameters through OPEN messages. KEEPALIVE messages maintain the session, while UPDATE messages exchange routing information. UDP, ICMP, and GRE are not used as the standard transport protocols for BGP peer sessions.

Question 322

Which OSPF component connects an OSPF area to the backbone area?

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

Correct Answer: 3

Explanation

An Area Border Router (ABR) connects one OSPF area to another and commonly connects non-backbone areas to Area 0, the OSPF backbone. An ABR maintains separate link-state information for its connected areas and can advertise summarized inter-area routes using Type 3 LSAs. An ASBR introduces external routes into OSPF, while DR and BDR roles are associated with multiaccess network segments. ABRs are therefore essential for hierarchical OSPF designs where multiple areas communicate through the backbone.

Question 323

Which switching behavior occurs when a switch receives a broadcast frame?

1. It forwards the frame only to the default gateway
2. It drops the frame unless the destination MAC is known
3. It forwards the frame out all ports in the same VLAN except the incoming port
4. It sends the frame to every VLAN

Correct Answer: 3

Explanation

A Layer 2 switch floods a broadcast frame out all appropriate ports within the same VLAN except the interface on which the frame was received. Broadcast traffic is therefore limited to the local Layer 2 broadcast domain. The switch does not normally forward the broadcast directly to the default gateway or other VLANs. This behavior allows devices within the same VLAN to receive broadcast-based protocols and services. Routers or Layer 3 boundaries generally prevent Layer 2 broadcasts from crossing into other broadcast domains.

Question 324

Which BGP attribute can be used to identify routes that should receive special policy treatment?

1. Community
2. Router ID
3. Weight
4. Origin

Correct Answer: 1

Explanation

The BGP Community attribute allows routes to be tagged with values that can be matched by routing policies. Administrators can use communities to group prefixes according to characteristics such as customer type, geographic region, routing preference, or export policy. Policies can then match these tags and apply actions consistently to many routes. This makes communities useful in large environments where managing individual prefixes would be inefficient. Router ID identifies a BGP speaker, Weight influences local path selection, and Origin describes how a route entered BGP.

Question 325

Which protocol prevents Layer 2 switching loops by placing redundant interfaces into a logical blocking state?

1. STP
2. DHCP
3. NAT
4. SNMP

Correct Answer: 1

Explanation

Spanning Tree Protocol (STP) prevents Layer 2 loops by calculating a loop-free topology and logically blocking redundant paths. Ethernet networks require loop prevention because redundant links can otherwise cause broadcast storms, duplicate frames, and MAC-table instability. STP keeps alternative paths available as backups and can transition them into forwarding when the active path fails. DHCP provides host configuration, NAT translates addresses, and SNMP provides network management. STP is therefore the fundamental Layer 2 protocol used to prevent switching loops.

Question 326

Which IPv6 mechanism uses Neighbor Solicitation messages to verify that an address is not already in use?

1. SLAAC
2. Router Discovery
3. Duplicate Address Detection
4. DHCPv6

Correct Answer: 3

Explanation

Duplicate Address Detection (DAD) uses IPv6 Neighbor Discovery messages to determine whether an address is already in use on the local link. Before an IPv6 interface begins using an address, it can send a Neighbor Solicitation for that address. If another device is already using the address, an appropriate response indicates a conflict and the address should not be assigned normally. DAD helps prevent duplicate IPv6 addresses. SLAAC provides automatic address configuration, while Router Discovery and DHCPv6 serve other configuration and discovery functions.

Question 327

Which BGP attribute is generally preferred when its value is lower and can influence route selection between multiple external links?

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

Correct Answer: 2

Explanation

The Multi-Exit Discriminator (MED) is commonly used to influence how a neighboring autonomous system selects an entry point when multiple connections are available. A lower MED is generally preferred when comparing applicable paths from the same neighboring autonomous system. MED is primarily associated with influencing inbound traffic into an autonomous system. Local Preference and Weight are normally used to influence outbound decisions within the local autonomous system. Communities provide route tagging and policy classification rather than directly representing a numeric path preference.

Question 328

Which command displays the current OSPF neighbors and their adjacency states?

1. show ip ospf neighbor
2. show ip route
3. show interfaces
4. show ip protocols

Correct Answer: 1

Explanation

The show ip ospf neighbor command displays information about OSPF neighbors, including neighbor IDs, states, dead timers, interface information, and designated-router relationships where applicable. It is one of the most useful commands for troubleshooting OSPF adjacency problems. Administrators can determine whether a neighbor has reached the Full state and identify potential issues involving timers, network types, authentication, or connectivity. Other commands provide routing-table or interface information, but show ip ospf neighbor specifically focuses on OSPF neighbor relationships.

Question 329

Which security feature can restrict access to a switch port based on permitted MAC addresses?

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

Correct Answer: 2

Explanation

Port Security allows administrators to restrict which MAC addresses can use a switch interface. It can define a maximum number of secure MAC addresses and specify actions when violations occur. Secure addresses can be configured manually or learned dynamically depending on the configuration. This feature is commonly deployed on access ports to limit unauthorized devices and reduce certain Layer 2 security risks. DHCP Snooping protects DHCP exchanges, DAI validates ARP traffic, and Root Guard protects the spanning-tree root role. Port Security directly controls MAC-based access.

Question 330

Which routing protocol uses a composite metric that can include bandwidth, delay, reliability, and load?

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

Correct Answer: 3

Explanation

Enhanced Interior Gateway Routing Protocol (EIGRP) uses a composite metric that can consider bandwidth, delay, reliability, and load. By default, EIGRP calculates its metric using bandwidth and delay, while reliability and load can be incorporated through appropriate metric configuration. This provides more flexibility than protocols that use a single metric such as hop count. OSPF uses cost, RIP uses hop count, and BGP relies on path attributes. EIGRP’s composite metric allows it to make routing decisions based on multiple characteristics of the path.

Question 331

Which protocol provides a mechanism for centralized collection of system messages from routers and switches?

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

Correct Answer: 1

Explanation

Syslog allows network devices to generate and send event messages to a centralized logging system. These messages can include interface state changes, authentication events, system warnings, routing events, and other operational information. Centralized Syslog collection helps administrators correlate events across multiple devices and supports troubleshooting, auditing, and security investigations. NTP is used for time synchronization, DNS performs name resolution, and DHCP provides network configuration. Syslog is therefore the appropriate technology for centralized collection and analysis of device event messages.

Question 332

Which BGP mechanism prevents a route learned from an external autonomous system from being accepted if the local AS number appears in its AS Path?

1. Route reflection
2. AS Path loop prevention
3. MED
4. Community filtering

Correct Answer: 2

Explanation

BGP uses the AS Path attribute to prevent routing loops between autonomous systems. When a BGP router receives an update, it examines the AS Path for its own autonomous system number. If the local AS number is already present, the router normally rejects the route because accepting it could create a routing loop. This mechanism is one of the fundamental safety features of inter-domain BGP routing. Route reflection addresses iBGP scalability, MED influences path selection, and communities provide policy tags.

Question 333

Which technology can provide multiple logical Layer 2 networks over a shared physical switching infrastructure?

1. VLAN
2. VRF
3. NTP
4. IP SLA

Correct Answer: 1

Explanation

VLAN technology allows administrators to create multiple logical Layer 2 networks over the same physical switching infrastructure. Each VLAN represents a separate broadcast domain, providing segmentation without requiring physically separate switches for every group. VLANs are commonly used to separate departments, user groups, voice traffic, guest networks, and management traffic. VRF provides Layer 3 routing separation rather than Layer 2 segmentation. NTP and IP SLA perform time synchronization and network measurement functions. VLANs are therefore the appropriate technology for logical Layer 2 segmentation.

Question 334

Which BGP path attribute can be used to make an outbound route less preferred by increasing the apparent AS-path length?

1. Local Preference
2. Weight
3. AS Path prepending
4. MED

Correct Answer: 3

Explanation

AS Path prepending adds additional copies of an autonomous system number to the AS Path of an advertised route. Because BGP generally prefers a shorter AS Path when earlier path-selection criteria are equal, adding extra AS numbers can make the route less attractive to neighboring networks. This technique is commonly used to influence inbound traffic when multiple external connections are available. Local Preference and Weight primarily influence outbound routing within an autonomous system, while MED uses a different mechanism to influence neighboring path selection.

Question 335

Which network protocol allows devices to obtain their current time from a centralized time source?

1. NTP
2. SNMP
3. RADIUS
4. TFTP

Correct Answer: 1

Explanation

Network Time Protocol (NTP) allows network devices to synchronize their clocks with configured time sources. Consistent time is important for interpreting logs, correlating security events, troubleshooting failures, and maintaining accurate operational records. An NTP hierarchy can be used so that devices synchronize with reliable upstream time sources and potentially provide time to other devices. SNMP is used for monitoring, RADIUS provides AAA services, and TFTP provides basic file transfer. NTP is specifically designed for maintaining accurate and synchronized system clocks.

Question 336

Which protocol can authenticate network administrators against a centralized server while separating authentication and authorization functions?

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

Correct Answer: 2

Explanation

TACACS+ is an AAA protocol commonly used to centrally authenticate and authorize network administrators. It separates authentication, authorization, and accounting functions, allowing organizations to control which commands individual administrators can execute. This makes TACACS+ particularly useful for administrative access to routers, switches, and other infrastructure devices. A centralized AAA server also simplifies account management and auditing. DHCP assigns addresses, DNS resolves names, and NTP synchronizes clocks. TACACS+ is therefore well suited to centralized and granular control of network-device administration.

Question 337

Which VXLAN component performs encapsulation of an Ethernet frame into a VXLAN packet?

1. VTEP
2. VTP
3. STP
4. BDR

Correct Answer: 1

Explanation

A VXLAN Tunnel Endpoint (VTEP) performs VXLAN encapsulation and decapsulation. When an Ethernet frame needs to cross the Layer 3 VXLAN underlay, the source VTEP encapsulates the frame in a VXLAN and UDP/IP header before forwarding it across the network. At the destination, another VTEP removes the encapsulation and forwards the original Ethernet frame toward the endpoint. VTP manages VLAN information, STP prevents switching loops, and BDR is an OSPF role. VTEPs are therefore essential components of VXLAN overlay networks.

Question 338

Which method allows a router to use a backup static route only when the primary route is removed from the routing table?

1. ECMP
2. Route redistribution
3. Floating static route
4. Route summarization

Correct Answer: 3

Explanation

A floating static route is configured with a higher administrative distance than the primary route. As long as the preferred route is available, the floating route is not installed as the active forwarding path. When the primary route disappears, the floating static route can become active and provide backup connectivity. This technique is useful for simple WAN redundancy and failover designs. ECMP uses multiple equal-cost paths at the same time, redistribution exchanges routes between protocols, and summarization combines multiple prefixes into a larger route.

Question 339

Which protocol is commonly used by network devices to advertise information about directly connected Cisco neighbors?

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

Correct Answer: 1

Explanation

Cisco Discovery Protocol (CDP) is a Cisco proprietary Layer 2 protocol that allows Cisco devices to advertise information about directly connected Cisco neighbors. Administrators can use CDP to discover details such as device identity, platform, software version, connected interface, and capabilities. This information is useful when documenting topology and troubleshooting physical connections. LLDP provides similar functionality through a vendor-neutral standard. DNS, DHCP, and NTP perform name resolution, address configuration, and time synchronization respectively. CDP is therefore the appropriate protocol for Cisco-specific neighbor discovery.

Question 340

Which network automation framework commonly uses YAML playbooks to define repeatable configuration tasks?

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

Correct Answer: 4

Explanation

Ansible is an automation framework that commonly uses YAML-based playbooks to define repeatable tasks and workflows. In network environments, administrators can use Ansible to configure multiple devices, collect operational information, apply standardized policies, and automate routine changes. YAML makes playbooks relatively easy to read and maintain, while Ansible modules handle interactions with managed devices. Python is a programming language, while NETCONF and RESTCONF are network-management protocols. Ansible can use protocols such as NETCONF and RESTCONF as part of its network automation workflows.