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Question 241:

Which OSPF feature allows a router to advertise a summarized range of routes from one area into another area?

1. OSPF authentication
2. Area range
3. Router ID
4. Passive interface

Correct Answer: 2

Explanation:

OSPF area summarization allows an Area Border Router to summarize multiple routes into a smaller number of prefixes when advertising information between areas. In Junos OS, an area range can be configured to represent a group of more-specific routes with a summarized prefix. This can reduce the amount of routing information propagated between areas and can make the routing table easier to manage. Summarization can also reduce the impact of topology changes by limiting the number of specific routes advertised outside the originating area. Router ID identifies the OSPF router, while authentication and passive interfaces serve different operational purposes.

Question 242:

Which OSPF timer determines how long a router waits without receiving Hello packets before declaring a neighbor down?

1. SPF timer
2. Retransmission interval
3. Dead interval
4. LSA refresh timer

Correct Answer: 3

Explanation:

The OSPF dead interval specifies how long a router can go without receiving valid Hello packets from a neighbor before considering that neighbor unavailable. The dead interval must be compatible between OSPF neighbors for an adjacency to form correctly. If Hello packets continue to arrive within the configured interval, the neighbor remains reachable from the OSPF perspective. If they stop for the entire dead interval, the router removes the neighbor relationship and recalculates the topology as necessary. This timer is therefore particularly useful when troubleshooting unstable OSPF adjacencies or unexpected neighbor removals.

Question 243:

When comparing otherwise eligible BGP routes, which local preference value is preferred?

1. Higher value
2. Lower value
3. Zero value
4. The oldest value

Correct Answer: 1

Explanation:

BGP local preference is used to influence outbound routing decisions within an autonomous system. When comparing otherwise eligible routes, a higher local-preference value is preferred. Administrators can therefore assign a higher value to routes learned through a preferred exit point and a lower value to routes learned through a backup path. Because local preference is propagated within the autonomous system, multiple BGP routers can make consistent outbound path-selection decisions. This makes local preference particularly useful for controlling which external connection carries outbound traffic. MED has a different purpose and is generally used to influence how another autonomous system enters a network.

Question 244:

What is the primary purpose of a BGP route reflector?

1. To replace OSPF SPF calculations
2. To reduce the need for a full iBGP mesh
3. To provide Layer 2 switching
4. To assign IP addresses to clients

Correct Answer: 2

Explanation:

A BGP route reflector reduces the requirement for a full mesh of internal BGP sessions. In a traditional iBGP design, routers generally need sessions with other iBGP routers to distribute routes effectively, which becomes difficult to scale as the number of routers increases. A route reflector can receive routes from clients and reflect eligible routes to other clients or nonclients according to BGP rules. This significantly simplifies large iBGP deployments. Route reflectors are a BGP scalability mechanism and do not replace OSPF SPF calculations, provide Layer 2 switching, or perform client IP address assignment.

Question 245:

Which BGP attribute helps prevent a route learned from an autonomous system from being accepted again by the same autonomous system?

1. MED
2. Community
3. AS Path
4. Local Preference

Correct Answer: 3

Explanation:

The BGP AS Path attribute provides an important loop-prevention mechanism. When a route is advertised through eBGP, the advertising router adds its autonomous system number to the AS Path. When another router receives the route, it can inspect the path and reject the route if its own AS number is already present. This prevents many routing loops between autonomous systems. Local preference is primarily used to influence outbound path selection within an AS, while MED can influence inbound path selection by a neighboring AS. Communities are tags used to communicate routing information and apply policy but do not directly provide the same AS-loop detection mechanism.

Question 246:

Which OSPF packet is used to advertise LSAs to neighboring routers?

1. Link State Update
2. Database Description
3. Link State Request
4. Hello

Correct Answer: 1

Explanation:

The OSPF Link State Update packet carries one or more Link State Advertisements and is used to distribute link-state information to neighboring routers. When a router generates or receives information that needs to be flooded, LSAs can be carried inside Link State Update packets. Database Description packets are used during database synchronization to summarize LSDB contents, while Link State Request packets ask a neighbor for specific LSAs. Hello packets are primarily used for neighbor discovery and maintaining OSPF relationships. Understanding these packet types is useful when troubleshooting OSPF adjacency formation and LSA flooding problems.

Question 247:

Which OSPF packet is primarily used to discover neighbors and maintain OSPF adjacencies?

1. Link State Update
2. Hello
3. Link State Request
4. Database Description

Correct Answer: 2

Explanation:

OSPF Hello packets are used to discover neighboring OSPF routers and maintain neighbor relationships. Hello packets contain important parameters such as the router ID, area information, timers, and network-related details. Routers periodically send Hellos on OSPF-enabled interfaces, allowing neighbors to determine whether communication is still active. If Hello packets stop arriving for the configured dead interval, the neighbor can be declared down. Database Description, Link State Request, and Link State Update packets are used primarily during LSDB synchronization and LSA exchange rather than initial neighbor discovery.

Question 248:

In OSPF, what is the main purpose of the Router ID?

1. To identify the OSPF router uniquely within the OSPF domain
2. To identify the physical interface speed
3. To determine the BGP local preference
4. To identify a VXLAN VNI

Correct Answer: 1

Explanation:

The OSPF Router ID uniquely identifies an OSPF router within the OSPF routing domain. It is represented as a 32-bit value and is commonly displayed in dotted-decimal notation. The Router ID is used in OSPF operations such as neighbor relationships, LSAs, and designated-router elections. It is not an IP address that necessarily has to be assigned to an active interface, although Junos can derive the Router ID from configured addresses when one is not explicitly configured. Interface speed, BGP local preference, and VXLAN VNI are separate concepts and do not determine the OSPF Router ID.

Question 249:

Which Junos command provides a concise summary of BGP peer status and the number of routes exchanged with peers?

1. show ospf database
2. show interfaces terse
3. show bgp summary
4. show arp

Correct Answer: 3

Explanation:

The show bgp summary command provides a concise overview of BGP sessions. It can show information such as the local router’s BGP details, peer addresses, autonomous-system information, session state, and route counts. This makes it one of the most useful initial commands when troubleshooting BGP connectivity or determining whether sessions are established. If a peer is not in an established state, additional commands can then be used to investigate configuration, TCP connectivity, authentication, or routing issues. The other commands serve different purposes: OSPF database inspection, interface status, and ARP information respectively.

Question 250:

Which Junos feature can automatically provide network-policy information to compatible IP phones using LLDP extensions?

1. LLDP-MED
2. RSTP
3. LACP
4. BGP

Correct Answer: 1

Explanation:

LLDP-MED provides extensions to LLDP that are specifically useful for endpoint devices such as IP phones. One important capability is Network Policy, which can communicate information such as the VLAN and QoS treatment intended for voice traffic. This can simplify IP telephony deployment because compatible phones can learn network information from the switch rather than requiring all settings to be manually configured. RSTP is used for Layer 2 loop prevention, LACP is used for link aggregation, and BGP is a routing protocol. LLDP-MED therefore provides the endpoint discovery and policy exchange capabilities relevant to IP phone deployments.

Question 251:

Which VLAN configuration is commonly used to separate IP phone traffic from ordinary data traffic on an access switch?

1. Voice VLAN
2. Management-only VLAN
3. VXLAN VNI
4. OSPF area

Correct Answer: 1

Explanation:

A voice VLAN provides a logical Layer 2 segment dedicated to IP phone traffic. Separating voice from ordinary data traffic allows administrators to apply appropriate security and Quality of Service policies to voice packets. An access port can be configured to support an attached phone while also allowing a connected computer to use a separate data VLAN, depending on the platform and configuration. Voice VLAN deployments are often combined with LLDP-MED to communicate voice network-policy information to compatible phones. A VXLAN VNI identifies an overlay segment, while an OSPF area is a routing-domain construct and not a VLAN mechanism.

Question 252:

What does a CoS drop profile primarily control?

1. How packets are authenticated
2. How packets may be dropped as congestion increases
3. How BGP neighbors are established
4. How OSPF Router IDs are selected

Correct Answer: 2

Explanation:

A CoS drop profile defines packet-drop behavior under congestion. As queue occupancy increases, the profile can determine the likelihood that packets with particular loss priorities will be discarded. This allows network administrators to protect higher-priority traffic while making lower-priority traffic more susceptible to dropping during congestion. Drop profiles are therefore an important component of congestion management. They work together with forwarding classes, packet-loss priority, queues, and schedulers. Authentication, BGP neighbor establishment, and OSPF Router ID selection are unrelated to drop profiles because those functions belong to network access control or routing protocols rather than Class of Service.

Question 253:

Which CoS component is responsible for enforcing a configured traffic rate and potentially dropping packets that exceed the allowed rate?

1. Policer
2. Scheduler
3. Router ID
4. Route reflector

Correct Answer: 1

Explanation:

A CoS policer enforces a configured traffic rate by monitoring the amount of traffic passing through a particular point. When traffic exceeds the configured limits, the policer can take actions such as dropping packets or changing their treatment, depending on the configuration. Policing is commonly used to control traffic entering a network or service and prevent a source from exceeding an agreed rate. A scheduler instead determines how queued traffic receives transmission resources, while a route reflector and Router ID belong to BGP and OSPF respectively. Understanding the distinction between policing and shaping is important when designing QoS behavior.

Question 254:

In an EVPN-VXLAN architecture, what is the primary role of the IP underlay?

1. Provide IP reachability between VTEPs
2. Assign MAC addresses to hosts
3. Perform user authentication
4. Replace the EVPN control plane

Correct Answer: 1

Explanation:

The IP underlay provides the basic IP connectivity required between VXLAN Tunnel Endpoints. VTEPs rely on this routed network to transport VXLAN-encapsulated packets between different locations. The underlay should therefore provide reliable IP reachability, while the EVPN control plane can distribute endpoint information such as MAC and IP reachability. The underlay does not itself replace the EVPN control plane or perform endpoint authentication. A well-designed VXLAN network separates the responsibilities of the underlay and overlay: the underlay provides transport connectivity, while the overlay provides logical segmentation and endpoint reachability.

Question 255:

Which EVPN route type is associated with Ethernet Auto-Discovery?

1. Route Type 4
2. Route Type 3
3. Route Type 1
4. Route Type 2

Correct Answer: 3

Explanation:

EVPN Route Type 1 is the Ethernet Auto-Discovery route. It is used in EVPN Ethernet segment and multihoming operations and can provide information needed for Ethernet segment discovery and related procedures. Route Type 2 is the MAC/IP Advertisement route, Route Type 3 is the Inclusive Multicast Ethernet Tag route, and Route Type 4 is the Ethernet Segment route. Knowing the EVPN route types is important for understanding how the control plane distributes Layer 2 reachability and multihoming information. In troubleshooting, identifying the expected route type can help determine whether the appropriate EVPN control-plane information is being exchanged.

Question 256:

Which EVPN route type is used to advertise inclusive multicast Ethernet Tag information?

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

Correct Answer: 4

Explanation:

EVPN Route Type 3 is known as the Inclusive Multicast Ethernet Tag route. It is used to advertise information needed for handling broadcast, unknown-unicast, and multicast traffic within an EVPN service. In VXLAN EVPN deployments, this information can help establish the necessary replication behavior between VTEPs for traffic that is not destined for a known unicast MAC address. Route Type 2 handles MAC/IP advertisements, Route Type 1 handles Ethernet Auto-Discovery, and Route Type 4 is associated with Ethernet segments. Understanding Type 3 is therefore important when troubleshooting BUM traffic across an EVPN-VXLAN overlay.

Question 257:

What is the primary purpose of EVPN designated-forwarder election in a multihomed Ethernet segment?

1. Determine which PE forwards certain traffic toward the multihomed segment
2. Select the BGP local preference
3. Assign an OSPF Router ID
4. Choose a VXLAN VNI

Correct Answer: 1

Explanation:

Designated-forwarder election is an important EVPN multihoming mechanism. When multiple PE devices are connected to the same Ethernet segment, forwarding certain traffic from the EVPN network toward that segment must be coordinated to avoid unnecessary duplication or loops. The designated-forwarder role identifies which PE is responsible for forwarding applicable traffic toward the multihomed Ethernet segment. EVPN uses control-plane information and Ethernet Segment identifiers to support this process. DF election does not determine BGP local preference, OSPF Router IDs, or VXLAN VNIs. Those values perform different functions within the routing and overlay architecture.

Question 258:

Which Junos command is commonly used to verify MAC address entries learned by an Ethernet switch?

1. show bgp summary
2. show ethernet-switching table
3. show ospf neighbor
4. show system uptime

Correct Answer: 2

Explanation:

The show ethernet-switching table command displays the Layer 2 MAC forwarding table on a Junos switching device. It can help administrators determine which MAC addresses have been learned and the interfaces or logical switching contexts associated with those entries. This command is useful when troubleshooting Layer 2 connectivity, unexpected MAC learning, or switching behavior. show bgp summary provides BGP peer information, show ospf neighbor displays OSPF adjacency information, and show system uptime reports system runtime information. Therefore, the Ethernet switching table is the appropriate place to inspect dynamically or statically learned MAC forwarding entries.

Question 259:

Which authentication server protocol is commonly used with Junos 802.1X and MAC-based authentication?

1. RADIUS
2. OSPF
3. VXLAN
4. LACP

Correct Answer: 1

Explanation:

RADIUS is commonly used as the authentication and authorization protocol for enterprise access-control mechanisms such as 802.1X and MAC-based authentication. A switch can communicate with a RADIUS server to validate endpoint credentials or identity information and receive authorization-related responses. This allows authentication decisions to be centralized instead of being configured independently for every access switch. OSPF is a routing protocol, VXLAN provides overlay networking, and LACP manages link aggregation. In an enterprise access-control architecture, RADIUS can therefore play an important role in determining whether an endpoint receives normal, restricted, guest, or other forms of network access.

Question 260:

Which Junos command is most useful for checking the current state and basic information of OSPF neighbors?

1. show ospf neighbor
2. show route forwarding-table
3. show bgp summary
4. show ethernet-switching table

Correct Answer: 1

Explanation:

The show ospf neighbor command provides information about OSPF neighbor relationships and their current states. It is one of the primary commands used when troubleshooting OSPF adjacency problems because it can show whether a neighbor is progressing through the expected states or has reached Full. Administrators can use this information to investigate issues involving interface configuration, Hello and dead timers, area mismatches, authentication, or network connectivity. The other commands are designed for different purposes: forwarding-table inspection, BGP session status, and Layer 2 MAC learning. Therefore, show ospf neighbor is the appropriate starting point for examining OSPF adjacency status.