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Question 341

Which IPv6 mechanism verifies an address is not duplicated?

1. Router Advertisement
2. Neighbor Solicitation
3. Prefix Delegation
4. Duplicate Address Detection

Correct Answer: 4

Explanation:

Duplicate Address Detection, commonly abbreviated DAD, verifies that an IPv6 address is not already being used by another node on the local network. Before an address becomes fully usable, the IPv6 node can send Neighbor Solicitation messages to determine whether another device responds for that address. If another node indicates ownership, the address is considered duplicated and should not be used normally. Router Advertisements provide configuration information, while Prefix Delegation distributes network prefixes. DAD is therefore specifically responsible for detecting duplicate IPv6 addresses before they create an addressing conflict.

Question 342

Which IPv6 message requests configuration information from local routers?

1. Neighbor Solicitation
2. Router Solicitation
3. Router Advertisement
4. Neighbor Advertisement

Correct Answer: 2

Explanation:

Router Solicitation is an ICMPv6 Neighbor Discovery message used by an IPv6 host to request router information from routers on the local network. A host can send a Router Solicitation instead of waiting for the next periodic Router Advertisement. The router may then respond with configuration information such as network prefixes and other parameters. Neighbor Solicitation and Neighbor Advertisement primarily support neighbor discovery and address resolution functions, while Router Advertisement carries information from routers toward hosts. Router Solicitation therefore provides the mechanism for hosts to actively request local router configuration information.

Question 343

Which IPv6 message announces router configuration to hosts?

1. Router Advertisement
2. Router Solicitation
3. Neighbor Solicitation
4. Redirect

Correct Answer: 1

Explanation:

Router Advertisement messages communicate IPv6 router and prefix information to hosts on a local network. They are part of the ICMPv6 Neighbor Discovery framework and can provide information used for automatic IPv6 configuration. Hosts can receive advertisements periodically or after sending Router Solicitation messages. Neighbor Solicitation is used for neighbor-related operations, while Redirect messages provide more specific routing guidance to hosts. Router Advertisement is therefore the message responsible for announcing router availability and relevant IPv6 network configuration information.

Question 344

Which IPv6 address category is intended for temporary privacy?

1. Link-local address
2. Global address
3. Temporary address
4. Multicast address

Correct Answer: 3

Explanation:

IPv6 temporary addresses are designed to reduce the ability to track a host based on a stable interface identifier. Privacy mechanisms can generate temporary addresses that change periodically while allowing the host to maintain normal IPv6 communication. Link-local addresses are used for communication on the local link, global addresses provide broader IPv6 reachability, and multicast addresses identify groups of receivers. Temporary addresses therefore serve a privacy-oriented purpose rather than defining a particular routing scope or multicast membership. Their use can help reduce long-term exposure of a stable host identifier.

Question 345

Which IPv6 mechanism advertises prefix information without DHCPv6?

1. Router Advertisement
2. Neighbor Advertisement
3. Router Solicitation
4. DHCP Relay

Correct Answer: 1

Explanation:

IPv6 Router Advertisement messages can provide hosts with prefix information needed for stateless address configuration. This allows a host to construct an IPv6 address using information received from the local router without requiring DHCPv6 for the address-generation process. Router Solicitation is used by hosts to request advertisements, while Neighbor Advertisement supports neighbor discovery. DHCP Relay forwards DHCP-related traffic between clients and servers. Router Advertisement is therefore the key mechanism for distributing IPv6 prefix information in stateless configurations.

Question 346

Which multicast version supports source filtering by receivers?

1. IGMPv1
2. IGMPv2
3. IGMPv3
4. IGMPv4

Correct Answer: 3

Explanation:

IGMPv3 introduces source filtering capabilities that allow IPv4 multicast receivers to express interest in traffic from specific sources. This capability supports source-specific multicast models and gives receivers greater control over which multicast streams they accept. Earlier IGMP versions provide simpler group-membership functionality and do not offer the same source-selection capabilities. IGMPv4 is not a standard version used for this purpose. IGMPv3 is therefore the appropriate version when source filtering and source-specific receiver behavior are required in IPv4 multicast networks.

Question 347

Which switching feature restricts forwarding based on learned MAC addresses?

1. MAC limiting
2. Route summarization
3. DHCP snooping
4. Prefix delegation

Correct Answer: 1

Explanation:

MAC limiting controls the number or set of MAC addresses that can be learned or used on a switching interface, depending on the configured Junos feature and policy. It can help restrict unauthorized devices and reduce certain Layer 2 security risks. Route summarization operates at the routing-table level, DHCP-related mechanisms concern host configuration, and prefix delegation concerns IPv6 network prefixes. MAC limiting therefore addresses Ethernet switching behavior by controlling acceptable MAC-address learning or usage on an interface. Its exact enforcement behavior depends on the configured limits and associated switching policies.

Question 348

Which Layer 2 feature prevents unauthorized switch connections?

1. Root protection
2. Port security
3. Link aggregation
4. Traffic shaping

Correct Answer: 2

Explanation:

Port security mechanisms can restrict which devices are permitted to use a switch interface by controlling acceptable MAC addresses or related access conditions. This can help prevent unauthorized endpoints from connecting to protected network ports. Root protection serves a different Layer 2 control-plane purpose by protecting spanning-tree topology, link aggregation combines physical links, and traffic shaping controls packet transmission rates. Port security therefore addresses endpoint access at the switch-port level. Proper configuration can help administrators enforce expected device connectivity while reducing the risk of unauthorized Layer 2 access.

Question 349

Which spanning-tree protection feature blocks unexpected root BPDUs?

1. BPDU filter
2. Loop protection
3. Root protection
4. MAC limiting

Correct Answer: 3

Explanation:

Root protection helps prevent a designated spanning-tree port from becoming influenced by unexpected superior BPDUs that could attempt to establish a different spanning-tree root. This protects the intended Layer 2 topology from unauthorized or unexpected root changes. BPDU filtering controls the handling of BPDUs, while loop protection addresses certain conditions involving missing BPDUs and Layer 2 loop prevention. MAC limiting concerns endpoint MAC-address restrictions rather than spanning-tree root selection. Root protection is therefore specifically associated with defending the intended root topology from inappropriate spanning-tree information.

Question 350

Which spanning-tree feature suppresses BPDU transmission or reception?

1. BPDU filter
2. Root protection
3. Loop protection
4. Storm control

Correct Answer: 1

Explanation:

BPDU filtering controls the handling of Bridge Protocol Data Units on configured switch interfaces. Depending on the specific configuration and platform behavior, it can prevent BPDUs from being processed or transmitted on selected ports. This differs from root protection, which is designed to prevent unexpected devices from influencing the spanning-tree root, and loop protection, which addresses certain loss-of-BPDU conditions. Storm control manages excessive Layer 2 traffic. BPDU filtering should therefore be used deliberately because suppressing spanning-tree control traffic can affect loop-prevention behavior.

Question 351

Which spanning-tree mechanism detects missing BPDUs on protected ports?

1. BPDU filter
2. Loop protection
3. Root protection
4. MAC limiting

Correct Answer: 2

Explanation:

Loop protection helps protect Layer 2 networks when expected BPDUs stop arriving on interfaces participating in spanning-tree operation. Under appropriate conditions, the feature can place a port into a protective state rather than allowing it to transition in a way that could create a forwarding loop. BPDU filtering serves a different purpose by controlling BPDU handling, while root protection focuses on preventing an unexpected superior root from influencing the topology. MAC limiting addresses endpoint restrictions. Loop protection is therefore specifically associated with detecting abnormal loss of expected spanning-tree control information.

Question 352

Which Ethernet service transports frames across a provider network?

1. VPLS
2. VRF
3. DHCP
4. RADIUS

Correct Answer: 1

Explanation:

Virtual Private LAN Service, or VPLS, provides Layer 2 connectivity between customer sites across a provider network. It allows geographically separated Ethernet segments to appear as part of a common virtual Layer 2 service. Customer frames can therefore traverse the provider infrastructure while maintaining Ethernet service characteristics. VRF provides separated Layer 3 routing tables, DHCP provides host configuration, and RADIUS handles centralized authentication. VPLS is consequently associated with delivering Layer 2 VPN connectivity across a provider network.

Question 353

Which EVPN identifier represents an Ethernet Segment?

1. Route Distinguisher
2. Ethernet Segment Identifier
3. Route Target
4. Virtual Network Identifier

Correct Answer: 2

Explanation:

The Ethernet Segment Identifier, or ESI, identifies an Ethernet segment in EVPN environments, particularly where multihoming is involved. It allows participating devices to recognize the same customer-facing Ethernet segment and coordinate forwarding behavior across redundant provider-edge connections. A Route Distinguisher separates VPN routes within routing tables, while a Route Target controls route import and export policy. A Virtual Network Identifier is associated with other virtual-network technologies. The ESI therefore has a specific role in identifying an Ethernet segment within EVPN architectures.

Question 354

Which EVPN route type advertises MAC and IP reachability?

1. Type 1
2. Type 2
3. Type 3
4. Type 5

Correct Answer: 2

Explanation:

EVPN Route Type 2 is used for MAC/IP Advertisement routes. These routes provide information about Ethernet endpoint reachability and can associate a MAC address with an IP address when applicable. Other EVPN route types perform different functions: Type 1 supports Ethernet Auto-Discovery, Type 3 handles inclusive multicast Ethernet-tag information, and Type 5 provides IP Prefix routes. Understanding EVPN route types is important when troubleshooting control-plane learning and determining how endpoint information is distributed between participating provider-edge devices.

Question 355

Which EVPN route type advertises IP prefixes independently of MACs?

1. Type 5
2. Type 2
3. Type 3
4. Type 1

Correct Answer: 1

Explanation:

EVPN Route Type 5 is used to advertise IP Prefix routes. Unlike Type 2 MAC/IP Advertisement routes, Type 5 routes allow IP prefix reachability to be distributed through the EVPN control plane without requiring the route to represent a specific MAC/IP endpoint advertisement. Type 1 is associated with Ethernet Auto-Discovery, while Type 3 carries Inclusive Multicast Ethernet Tag information. Type 5 is therefore particularly relevant to integrated Layer 2 and Layer 3 EVPN designs where routed prefixes need to be advertised through the EVPN control plane.

Question 356

Which VPN attribute distinguishes identical customer prefixes?

1. Route Target
2. Route Distinguisher
3. Community
4. Cluster List

Correct Answer: 2

Explanation:

A Route Distinguisher, or RD, makes otherwise identical VPN prefixes unique within the provider’s VPN routing infrastructure. This is especially important when different customers use overlapping address spaces. By adding the RD to a customer prefix, the resulting VPN route becomes distinguishable from an identical prefix belonging to another VPN. Route Targets serve a different purpose by controlling which VPN routes are imported or exported. Community and Cluster List are BGP-related attributes with other policy and route-reflection functions. The RD therefore provides uniqueness rather than controlling route distribution policy.

Question 357

Which VPN attribute controls import and export membership?

1. Route Target
2. Route Distinguisher
3. AS Path
4. MED

Correct Answer: 1

Explanation:

A Route Target, or RT, is used to control which VPN routes are imported into or exported from particular VPN routing instances. By assigning compatible Route Target values, administrators can determine which customer sites or VPN instances should share specific routes. This differs from the Route Distinguisher, which primarily makes overlapping VPN prefixes unique. AS Path and MED are BGP path attributes serving different purposes. Route Targets are therefore central to controlling VPN route distribution and defining which routing instances participate in particular VPN connectivity relationships.

Question 358

Which MPLS mode retains labels learned from alternate next hops?

1. Conservative retention
2. Liberal retention
3. Strict retention
4. Selective retention

Correct Answer: 2

Explanation:

Liberal label retention allows an MPLS router to retain label bindings learned from neighboring label distribution peers even when those bindings are not currently associated with the router’s selected next hop. Keeping these bindings can make label information immediately available if the preferred path changes. Conservative label retention keeps a narrower set of label bindings associated with active forwarding requirements. The distinction affects label availability and resource usage. Liberal retention can provide faster readiness after topology changes because previously learned alternate label information does not necessarily need to be relearned.

Question 359

Which LDP distribution method sends labels without explicit requests?

1. Downstream on Demand
2. Downstream Unsolicited
3. Upstream Requested
4. Selective Advertisement

Correct Answer: 2

Explanation:

In Downstream Unsolicited label distribution, an LDP router can advertise label bindings to its neighbors without first receiving an explicit request for each binding. This allows label information to be distributed proactively and is a common concept in MPLS label distribution. Downstream on Demand follows a different model in which label information is requested when needed. The distinction affects how quickly label bindings become available and how signaling exchanges are performed. Downstream Unsolicited therefore represents proactive label advertisement rather than request-driven label distribution.

Question 360

Which MPLS concept identifies packets receiving identical forwarding treatment?

1. Label Binding
2. Forwarding Equivalence Class
3. Label Space
4. LDP Session

Correct Answer: 2

Explanation:

A Forwarding Equivalence Class, or FEC, groups packets that receive the same forwarding treatment through an MPLS network. Packets belonging to the same FEC can therefore be assigned and handled using common forwarding information. A label binding associates an MPLS label with a particular forwarding context, while label space refers to the scope in which labels are meaningful. An LDP session provides the control-plane relationship used to exchange label information. The FEC is therefore the concept that defines which packets should receive equivalent forwarding behavior.