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Question 281:

Which OSPF LSA type is used to describe the links and networks within a router’s own area?

1. Type 1 Router LSA
2. Type 3 Summary LSA
3. Type 4 ASBR Summary LSA
4. Type 5 AS External LSA

Correct Answer: 1

Explanation:

An OSPF Type 1 Router LSA is generated by each OSPF router to describe its active links and the state of those links within an area. These LSAs are flooded throughout the originating area and form an important part of the link-state database used by OSPF routers when calculating shortest paths. Type 3 LSAs are used by ABRs to advertise inter-area networks, Type 4 LSAs identify paths to ASBRs, and Type 5 LSAs carry external routing information. Understanding LSA types is important when troubleshooting missing routes or unexpected OSPF topology information.

Question 282:

Which OSPF LSA type is generated by a designated router on a multiaccess network to describe the attached routers and network?

1. Type 5
2. Type 2
3. Type 3
4. Type 7

Correct Answer: 2

Explanation:

A Type 2 Network LSA is generated by the designated router on a multiaccess OSPF network. It represents the shared network segment and identifies the routers attached to that segment. Type 2 LSAs are flooded within the originating area and help OSPF routers build an accurate representation of the shared topology. A Type 1 Router LSA describes an individual router’s links, while Type 3 Summary LSAs provide inter-area information. Type 5 LSAs are used for external routes. Type 2 LSAs are therefore especially relevant when examining OSPF operation on Ethernet segments where DR and BDR elections take place.

Question 283:

Which OSPF LSA type is commonly used by an ABR to advertise networks from one area into another area?

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

Correct Answer: 3

Explanation:

Type 3 Summary LSAs are generated by an OSPF Area Border Router to advertise network reachability information between OSPF areas. They allow routers in one area to learn about networks located in another area without requiring every router to maintain the complete topology of all areas. This supports OSPF scalability through its hierarchical area architecture. Type 1 LSAs describe individual routers, Type 2 LSAs describe multiaccess networks, and Type 5 LSAs advertise external routes. When troubleshooting inter-area routing, checking whether the expected Type 3 LSAs exist can help determine whether the ABR is correctly advertising the required prefixes.

Question 284:

Which OSPF LSA type provides information about the location of an ASBR to routers in other areas?

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

Correct Answer: 3

Explanation:

An OSPF Type 4 ASBR Summary LSA provides information that allows routers in another area to determine how to reach an Autonomous System Boundary Router. This becomes important when external routes originated by an ASBR need to be accessed from another OSPF area. The Type 4 LSA identifies the ASBR and provides the information needed to reach it through the OSPF domain. Type 1 LSAs describe routers within an area, Type 2 describes broadcast or multiaccess networks, and Type 3 advertises inter-area network information. Understanding Type 4 LSAs is particularly useful when troubleshooting external route reachability across OSPF areas.

Question 285:

Which OSPF LSA type is commonly used to advertise external routes into an OSPF domain?

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

Correct Answer: 1

Explanation:

Type 5 AS External LSAs are used to advertise routes that originate outside the OSPF autonomous system. An ASBR can redistribute external routing information into OSPF, and the resulting Type 5 LSAs can be flooded throughout the OSPF domain, subject to area restrictions. These routes can represent destinations learned through another routing protocol or configured through another mechanism. Type 1 and Type 2 LSAs describe internal topology, while Type 3 LSAs provide inter-area network information. When an external destination is missing from an OSPF routing table, examining the relevant Type 5 LSA and the ASBR’s reachability can help identify the problem.

Question 286:

What is the main purpose of an OSPF stub area?

1. To eliminate all OSPF adjacencies
2. To reduce the amount of external routing information carried into the area
3. To replace the OSPF backbone
4. To disable SPF calculations

Correct Answer: 2

Explanation:

An OSPF stub area is designed to reduce the amount of external routing information that needs to be carried within the area. Instead of receiving detailed external routes through Type 5 LSAs, routers in a stub area can rely on a default route provided by the appropriate ABR for destinations outside the area. This can simplify the routing database and reduce unnecessary routing information. Stub areas still participate fully in OSPF for their internal and inter-area routing requirements. They do not eliminate OSPF adjacencies, replace Area 0, or disable SPF calculations. Stub-area design is therefore mainly a scalability and routing-information optimization.

Question 287:

Which OSPF area must normally connect all other standard OSPF areas in a hierarchical design?

1. Area 1
2. Area 10
3. Area 100
4. Area 0

Correct Answer: 4

Explanation:

Area 0 is the OSPF backbone area and serves as the central area for inter-area routing in a standard hierarchical OSPF design. Other OSPF areas normally connect to the backbone through Area Border Routers. The backbone allows routing information to be exchanged between different areas while maintaining OSPF’s hierarchical structure. An ABR can belong to Area 0 and one or more other areas. Although OSPF supports specific designs for special circumstances, a properly planned enterprise deployment generally uses Area 0 as the central backbone. Understanding the role of Area 0 is essential when designing and troubleshooting multi-area OSPF networks.

Question 288:

What is the primary advantage of dividing a large OSPF network into multiple areas?

1. It eliminates the need for routing policies
2. It reduces the scope of link-state information and SPF calculations
3. It removes the need for a backbone
4. It converts OSPF into BGP

Correct Answer: 2

Explanation:

Multiple OSPF areas help improve scalability by limiting the scope of detailed link-state information and topology changes. Routers maintain detailed LSDB information for their own areas, while ABRs exchange summarized or inter-area routing information between areas. This can reduce the amount of topology information that must be processed and can limit the scope of SPF calculations after certain changes. A multi-area design does not eliminate routing policies, remove the requirement for a backbone in a standard design, or convert OSPF into BGP. Proper area design is therefore an important consideration when building large enterprise routing environments.

Question 289:

Which OSPF process is responsible for calculating the shortest paths after the LSDB has been populated?

1. SPF calculation
2. BGP route reflection
3. MAC learning
4. VXLAN encapsulation

Correct Answer: 1

Explanation:

OSPF uses the Shortest Path First algorithm to calculate routes based on the information contained in the link-state database. The SPF calculation constructs a shortest-path tree with the local router as the root and determines the best paths to known destinations. Changes in topology can cause OSPF to update its LSDB and perform another SPF calculation. This is one reason why excessive topology changes can affect router processing. BGP route reflection, MAC learning, and VXLAN encapsulation are unrelated processes performed by different networking mechanisms. Understanding SPF behavior is essential when analyzing OSPF route selection and convergence.

Question 290:

Which Junos command is useful for checking the routes installed in the routing table and the protocols that contributed them?

1. show route
2. show lldp neighbors
3. show ethernet-switching table
4. show system users

Correct Answer: 1

Explanation:

The show route command displays information about routes in the Junos routing table. The output can provide details such as destination prefixes, next hops, protocol information, route preference, and active-route status. This makes the command useful for troubleshooting routing decisions and verifying whether expected routes have been installed. Administrators can also use more specific forms of the command to inspect particular protocols or prefixes. LLDP commands provide neighbor discovery information, the Ethernet switching table displays Layer 2 MAC entries, and system-user commands provide user information. Therefore, show route is a fundamental command for Layer 3 routing troubleshooting.

Question 291:

What is the purpose of the BGP next-hop attribute?

1. Identify the address that should be used to reach the advertised destination
2. Identify the BGP autonomous system number
3. Determine the OSPF dead interval
4. Identify the EVPN route type

Correct Answer: 1

Explanation:

The BGP next-hop attribute identifies the IP address that should be used as the next-hop destination when forwarding traffic toward a BGP-advertised prefix. Whether the next hop is changed or preserved depends on the BGP session type and configuration, including policies and features such as next-hop self. If a BGP route is received but its next hop is unreachable, the route may not be usable for forwarding. Therefore, checking next-hop reachability is an important part of BGP troubleshooting. The next-hop attribute is separate from the AS Path, local preference, MED, and community attributes, each of which serves a different role in route selection or policy.

Question 292:

What is the main purpose of configuring BGP next-hop self on a router?

1. To change the advertised route’s next hop to the local router
2. To disable BGP route advertisements
3. To change the route’s AS Path to zero
4. To convert eBGP into OSPF

Correct Answer: 1

Explanation:

BGP next-hop self causes a router to advertise itself as the next hop for routes it advertises to a BGP neighbor, when the feature is configured in the applicable policy or protocol context. This can be particularly useful in iBGP designs where an internal router receives an external route but other iBGP routers do not have direct reachability to the original external next hop. By making the local router the next hop, forwarding can be directed through a router that has the necessary external connectivity. Next-hop self does not disable BGP advertisements or modify the route into an OSPF route. It specifically addresses next-hop reachability.

Question 293:

Which BGP attribute is commonly used to influence outbound traffic within an autonomous system?

1. MED
2. Local Preference
3. Origin
4. Community-only

Correct Answer: 2

Explanation:

Local Preference is commonly used to influence outbound traffic within an autonomous system. A higher local-preference value is normally preferred when comparing otherwise eligible BGP paths. Administrators can use routing policies to assign higher values to preferred external connections and lower values to backup paths. Because local preference is carried through the AS, multiple internal BGP routers can make consistent outbound routing decisions. MED is primarily intended to influence how a neighboring AS selects an entry point, while Origin provides information about route origination. Communities are tags that can be used by policy but do not themselves represent a direct path-selection preference in the same way.

Question 294:

Which BGP attribute can be used to tag routes so that routing policies can identify groups of prefixes?

1. Community
2. Next Hop
3. Router ID
4. AS Path length only

Correct Answer: 1

Explanation:

BGP communities are attributes that can be attached to routes as tags. Routing policies can then match those communities and apply actions to groups of routes. This is especially useful in larger networks where administrators need to apply the same policy behavior to many prefixes without creating separate matching rules for each prefix. Communities can be used to identify customer routes, preferred routes, routes intended for specific peers, or routes that require special handling. The next-hop attribute identifies forwarding reachability, while Router ID identifies a BGP speaker. AS Path serves route-selection and loop-prevention purposes rather than providing the same flexible tagging mechanism.

Question 295:

Which EVPN route type advertises IP prefix reachability independently of a specific MAC address?

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

Correct Answer: 3

Explanation:

EVPN Route Type 5 is known as the IP Prefix route. It allows EVPN to advertise IP prefix reachability through the BGP EVPN control plane without requiring the advertisement to represent a specific MAC/IP endpoint in the same way as Route Type 2. This is useful for Layer 3 EVPN services and integrated routing designs where IP prefixes need to be distributed across the EVPN domain. Route Type 1 is Ethernet Auto-Discovery, Type 2 is MAC/IP Advertisement, and Type 3 is Inclusive Multicast Ethernet Tag. Understanding Type 5 is helpful when troubleshooting EVPN Layer 3 reachability and distributed routing designs.

Question 296:

Which EVPN route type is primarily associated with MAC/IP advertisement for endpoint reachability?

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

Correct Answer: 4

Explanation:

EVPN Route Type 2 is the MAC/IP Advertisement route and is one of the most important route types in EVPN deployments. It advertises endpoint MAC addresses and can include associated IP addresses. Remote EVPN devices can use this information to determine where a particular endpoint is reachable without relying exclusively on traditional Layer 2 flooding. This control-plane learning improves scalability and convergence in EVPN environments. Route Type 1 is used for Ethernet Auto-Discovery, Type 3 for Inclusive Multicast Ethernet Tag information, Type 4 for Ethernet Segment information, and Type 5 for IP Prefix advertisements.

Question 297:

Which protocol is used by LACP to dynamically negotiate and maintain link aggregation between compatible devices?

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

Correct Answer: 1

Explanation:

The Link Aggregation Control Protocol (LACP) is used to dynamically negotiate and maintain an aggregated link between compatible network devices. Multiple physical Ethernet links can be combined into a logical interface, such as an aggregated Ethernet interface, to provide increased bandwidth and redundancy. LACP exchanges control information between devices to determine which links can participate in the aggregation. OSPF and BGP are routing protocols, while RADIUS provides authentication and authorization services. LACP therefore operates at the link aggregation level rather than at the routing or user-authentication level.

Question 298:

What is a major benefit of using an aggregated Ethernet interface?

1. It combines multiple physical links into one logical interface
2. It eliminates all routing protocols
3. It assigns BGP communities automatically
4. It replaces the OSPF LSDB

Correct Answer: 1

Explanation:

An aggregated Ethernet interface combines multiple physical Ethernet links into a single logical interface. This can provide additional bandwidth and redundancy compared with relying on one physical link. LACP can be used to dynamically manage the member links and detect certain link-level changes. From the perspective of higher-layer configuration, the aggregated interface can be treated as a logical interface, simplifying network configuration. Link aggregation does not eliminate routing protocols, automatically assign BGP communities, or replace the OSPF link-state database. It primarily improves physical connectivity by bundling multiple links into a logical connection.

Question 299:

Which Junos command is useful for verifying the operational status and configuration details of an interface in greater detail?

1. show interfaces extensive
2. show route summary
3. show ospf database
4. show bgp summary

Correct Answer: 1

Explanation:

The show interfaces extensive command provides detailed operational and configuration-related information about network interfaces. It can display interface state, statistics, errors, physical characteristics, counters, and other information useful for troubleshooting connectivity or performance problems. Compared with show interfaces terse, the extensive form provides substantially more detail. show route summary focuses on routing information, show ospf database examines OSPF LSAs, and show bgp summary provides BGP peer information. When an interface appears operationally problematic, examining its detailed counters and state with show interfaces extensive can help identify physical or logical issues.

Question 300:

Which Junos operational command is most appropriate for checking the MAC addresses learned on a switching interface or VLAN?

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

Correct Answer: 3

Explanation:

The show ethernet-switching table command displays Layer 2 MAC address learning information on Junos switching devices. Administrators can use it to determine whether the switch has learned a particular MAC address and where that address is associated within the switching environment. This is useful when troubleshooting Layer 2 connectivity, unexpected flooding, MAC movement, or endpoint learning problems. show ospf neighbor is used for OSPF adjacency information, show bgp neighbor provides BGP peer details, and show system uptime reports system runtime. Therefore, the Ethernet switching table is the appropriate command for investigating MAC learning.