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Question 201:

Which OSPF mechanism is used to advertise information about directly connected links and networks?

1. BGP Update
2. Link-State Advertisement
3. RADIUS request
4. LLDP frame

Correct Answer: 2

Explanation:

OSPF uses Link-State Advertisements, or LSAs, to distribute information about links, networks, and other topology information throughout an OSPF area. Routers receive LSAs and use them to build their Link-State Database. The SPF algorithm then uses the database to calculate the shortest paths to reachable destinations. Different OSPF LSA types carry different kinds of information, depending on their purpose and location within the OSPF topology. Reliable LSA flooding is essential for maintaining a consistent topology view between routers. If LSAs are missing or incorrect, routers may calculate incomplete or unexpected paths. Therefore, examining the LSDB can be useful when troubleshooting OSPF routing problems.

Question 202:

Which OSPF packet is used to reliably acknowledge receipt of link-state information?

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

Correct Answer: 3

Explanation:

OSPF uses Link State Acknowledgment packets to acknowledge the receipt of Link-State Advertisements. OSPF relies on reliable flooding to ensure that important link-state information reaches neighboring routers correctly. When a router receives an LSA, the appropriate acknowledgment mechanism helps confirm that the information was received. This contributes to maintaining consistent LSDB information throughout an OSPF area. Hello packets are used primarily for neighbor discovery and maintenance, while Database Description packets summarize LSDB contents during adjacency formation. Link State Update packets carry actual LSAs. Understanding the different OSPF packet types is useful when analyzing packet captures or troubleshooting neighbors that fail during database synchronization.

Question 203:

What happens when an OSPF router receives a newer version of an LSA than the one currently stored in its LSDB?

1. It ignores the LSA permanently
2. It updates its LSDB and floods the newer information as appropriate
3. It converts the LSA into a BGP route
4. It removes the OSPF neighbor

Correct Answer: 2

Explanation:

When an OSPF router receives a newer version of an LSA, it updates the corresponding information in its Link-State Database and can flood the newer LSA to other appropriate OSPF neighbors. This allows routers within the area to maintain a consistent view of the network topology. OSPF uses sequence numbers and other LSA information to determine which advertisement is newer. Reliable flooding ensures that topology changes propagate through the OSPF domain. If routers retained outdated LSAs, they could calculate incorrect paths and create inconsistent routing behavior. Proper LSA synchronization is therefore fundamental to the operation and convergence of OSPF.

Question 204:

Which OSPFv3 feature allows it to operate using IPv6?

1. IPv6 packet transport
2. IPv4-only next hops
3. MAC RADIUS
4. VXLAN encapsulation

Correct Answer: 1

Explanation:

OSPFv3 is the OSPF version designed to support IPv6 routing. Unlike OSPFv2, which uses IPv4, OSPFv3 operates using IPv6 packet transport and IPv6 addressing mechanisms. Neighbor discovery and communication use IPv6 link-local addresses on enabled interfaces. OSPFv3 also separates certain addressing information from the core link-state topology information, allowing the protocol to represent IPv6 connectivity effectively. When troubleshooting OSPFv3, administrators should verify IPv6 interface configuration, link-local addressing, area configuration, and neighbor relationships. OSPFv3 does not depend on VXLAN, RADIUS, or MAC authentication for its basic routing operation.

Question 205:

Which BGP attribute identifies the origin of a route within the BGP route-selection process?

1. Origin
2. Community
3. Local preference
4. Next hop

Correct Answer: 1

Explanation:

The BGP Origin attribute indicates how a route was introduced into BGP. Common origin values represent routes learned through different mechanisms, such as an IGP-derived network statement, redistribution, or aggregation. The origin attribute can participate in BGP path selection when comparing otherwise eligible routes. In general, an IGP-originated route is preferred over an EGP-originated route, which is preferred over an incomplete origin. Administrators can inspect the origin attribute when analyzing why one BGP route was selected over another. The attribute is different from local preference, which influences outbound path selection, and next hop, which identifies the forwarding destination.

Question 206:

Which BGP path attribute is used to identify the IP address toward which traffic for a route should be forwarded?

1. Community
2. Next hop
3. Origin
4. MED

Correct Answer: 2

Explanation:

The BGP Next Hop attribute identifies the IP address that should be used as the forwarding next hop for a BGP route. For a route to be usable, the receiving router must have a valid route to that next-hop address. Next-hop behavior differs depending on the type of BGP session and configuration, so administrators should understand how next-hop information is propagated or modified in their design. If a BGP route appears in protocol information but is not installed as an active route, next-hop reachability is one of the important items to investigate. Checking the routing table alongside BGP information can help identify next-hop resolution problems.

Question 207:

Which BGP attribute can be used to influence the path selection of traffic entering an autonomous system from a neighboring AS?

1. Local preference
2. MED
3. Router ID
4. VNI

Correct Answer: 2

Explanation:

MED, or Multi-Exit Discriminator, can be used to influence which entry point a neighboring autonomous system prefers when multiple connections exist between the two autonomous systems. A lower MED is generally preferred when the relevant BGP comparison is made. Network administrators can set MED values using routing policies to indicate a preferred ingress connection. MED is primarily useful for influencing inbound traffic from a neighboring network, while local preference is normally used internally to influence outbound path selection. Because actual BGP route selection depends on multiple attributes and implementation details, MED should be considered as part of the complete routing policy rather than as an isolated mechanism.

Question 208:

Which BGP attribute is commonly used to identify routes that should receive a particular routing policy treatment?

1. Community
2. OSPF cost
3. VNI
4. ESI

Correct Answer: 1

Explanation:

BGP communities allow administrators to attach classification information to routes so that routing policies can identify and process them consistently. A community can represent a particular routing intention, customer category, traffic-engineering requirement, or filtering condition. A policy can match the community and then accept, reject, modify, or advertise the route according to the desired behavior. This approach is much more scalable than creating separate policy terms for every individual prefix. Communities are therefore widely used in service-provider and enterprise BGP designs. They do not directly determine the forwarding interface or VXLAN segment; their primary role is to provide information that can be used during routing-policy processing.

Question 209:

What is the primary purpose of an eBGP session?

1. Exchange routing information between different autonomous systems
2. Synchronize OSPF LSDBs
3. Authenticate Ethernet endpoints
4. Assign VLAN membership

Correct Answer: 1

Explanation:

External BGP, or eBGP, is used to exchange routing information between routers belonging to different autonomous systems. It is commonly deployed between an enterprise and an ISP, between service providers, or between organizations that need to exchange external routing information. eBGP provides the mechanism for advertising reachable prefixes and receiving routes from another autonomous system. Routing policies are normally applied to control which routes are accepted and advertised. This is different from iBGP, which exchanges BGP information between routers within the same autonomous system. Proper AS configuration and IP reachability are required before an eBGP session can successfully establish.

Question 210:

Which BGP session type is normally used to distribute BGP routes between routers inside the same autonomous system?

1. eBGP
2. iBGP
3. OSPF
4. LLDP

Correct Answer: 2

Explanation:

Internal BGP, or iBGP, is used to distribute BGP routing information among BGP speakers within the same autonomous system. An organization may use eBGP to learn routes from external providers and then use iBGP to distribute those routes to other internal routers. Traditional iBGP designs require a full mesh of sessions, although route reflectors can be used to improve scalability. iBGP has specific rules concerning route advertisement and next-hop behavior, making proper design important in larger networks. It is different from eBGP, where the participating routers belong to different autonomous systems.

Question 211:

Which EVPN route type is used for Inclusive Multicast Ethernet Tag information?

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

Correct Answer: 3

Explanation:

EVPN route type 3 is the Inclusive Multicast Ethernet Tag route. It provides control-plane information used to support the distribution of broadcast, unknown unicast, and multicast traffic across an EVPN environment. In a VXLAN EVPN fabric, this information can help VTEPs determine how traffic should be replicated across the overlay. Route type 3 has a different purpose from route type 2, which advertises MAC/IP reachability, and route type 4, which advertises Ethernet Segment information. Understanding EVPN route types is important when troubleshooting BUM traffic because missing or incorrect inclusive multicast information can affect the ability of VTEPs to distribute such traffic across the fabric.

Question 212:

Which EVPN route type advertises Ethernet Auto-Discovery information?

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

Correct Answer: 1

Explanation:

EVPN route type 1 is the Ethernet Auto-Discovery route. It provides information associated with Ethernet segments and is particularly relevant to EVPN multihoming. Ethernet Auto-Discovery information allows participating PE devices to advertise information about the Ethernet segments to which they are connected. This information supports redundancy and forwarding coordination in multihomed environments. Route type 2 is used for MAC/IP advertisement, route type 3 provides Inclusive Multicast Ethernet Tag information, and route type 4 advertises Ethernet Segment information. Knowing these distinctions is important when examining BGP EVPN routes and troubleshooting endpoint reachability or multihoming behavior.

Question 213:

What is the main purpose of EVPN route type 5?

1. Advertising IP prefix reachability
2. Advertising Ethernet Segment information
3. Advertising MAC-only reachability
4. Advertising LLDP neighbors

Correct Answer: 1

Explanation:

EVPN route type 5 is used to advertise IP prefix reachability. It allows EVPN networks to distribute Layer 3 routing information through the EVPN control plane, supporting scenarios where IP prefixes need to be advertised independently of individual MAC/IP host advertisements. This is particularly useful in EVPN-based Layer 3 VPN or integrated routing designs. Route type 5 should be distinguished from route type 2, which primarily provides MAC/IP advertisement information for individual endpoints. Understanding route type 5 is important when troubleshooting Layer 3 EVPN connectivity because the presence or absence of appropriate IP prefix routes can determine whether remote networks are reachable through the EVPN overlay.

Question 214:

Which EVPN mechanism helps prevent duplicate forwarding toward a multihomed Ethernet segment?

1. Designated Forwarder election
2. BGP local preference
3. OSPF SPF
4. RADIUS authentication

Correct Answer: 1

Explanation:

Designated Forwarder election helps coordinate which PE device forwards certain broadcast, unknown unicast, and multicast traffic toward a multihomed Ethernet segment. Without this coordination, multiple PEs could independently forward the same traffic toward the customer segment, potentially causing duplicate frames and Layer 2 loops. EVPN uses Ethernet Segment information and related control-plane mechanisms to coordinate the participating PEs. DF election is therefore an important component of EVPN multihoming. It should not be confused with BGP local preference or OSPF SPF, which influence Layer 3 routing decisions, or RADIUS, which provides authentication and authorization functions.

Question 215:

Which component of a VXLAN EVPN fabric performs encapsulation and decapsulation of VXLAN traffic?

1. Route reflector
2. VTEP
3. RADIUS server
4. OSPF ABR

Correct Answer: 2

Explanation:

A VXLAN Tunnel Endpoint, or VTEP, is responsible for VXLAN encapsulation and decapsulation. When local Ethernet traffic needs to cross the VXLAN overlay, the source VTEP encapsulates the original frame in a VXLAN/UDP/IP packet and sends it through the IP underlay. The destination VTEP removes the VXLAN encapsulation and forwards the original frame toward the appropriate local destination. VTEPs therefore form the boundary between the local network and the VXLAN overlay. EVPN can provide the control-plane information required to determine where remote endpoints are located, while the VTEPs perform the actual data-plane encapsulation and decapsulation.

Question 216:

Which identifier is carried in a VXLAN header to identify the logical overlay network?

1. BGP AS number
2. OSPF router ID
3. VNI
4. ESI

Correct Answer: 3

Explanation:

The VXLAN Network Identifier, or VNI, identifies the logical VXLAN segment to which an encapsulated packet belongs. It allows multiple virtual networks to share the same physical IP underlay while remaining logically separated. The VNI is carried in the VXLAN header and is used by the receiving VTEP to determine the appropriate virtual network for the decapsulated traffic. VNIs provide a much larger segmentation space than traditional VLAN identifiers, which makes VXLAN suitable for large data-center environments. The VNI should not be confused with an ESI, which identifies an Ethernet segment in EVPN multihoming, or a BGP AS number, which identifies an autonomous system.

Question 217:

Which CoS component is responsible for assigning incoming traffic to a forwarding class?

1. Scheduler
2. Classifier
3. Shaper
4. Drop profile

Correct Answer: 2

Explanation:

A CoS classifier examines characteristics of incoming packets and determines the appropriate forwarding class and packet loss priority. Classification can use packet markings such as DSCP or 802.1p, depending on the configured classifier. Once traffic has been classified, it can be placed into the appropriate queue and receive the forwarding treatment associated with that class. A scheduler determines how queued traffic receives transmission resources, while a shaper controls the transmission rate. A drop profile influences packet-loss behavior during congestion. Correct classification is therefore essential because it determines the subsequent CoS treatment applied to different types of traffic.

Question 218:

Which CoS mechanism controls the rate at which traffic is transmitted while generally allowing excess traffic to be buffered?

1. Policer
2. Shaper
3. Classifier
4. Rewrite rule

Correct Answer: 2

Explanation:

A traffic shaper controls the rate at which traffic is transmitted and can generally buffer traffic that temporarily exceeds the configured transmission rate. This smooths bursts and provides a more controlled traffic flow. Shaping is particularly useful when traffic needs to conform to a specific bandwidth rate before entering another network segment or service. A policer also enforces a traffic rate but can take immediate actions such as dropping or remarking packets that exceed the configured rate. Classifiers determine traffic categories, while rewrite rules modify packet markings. Understanding these distinctions is important when designing and troubleshooting Junos CoS policies.

Question 219:

Which CoS value indicates that traffic is more eligible to be dropped during congestion?

1. Low packet loss priority
2. High packet loss priority
3. Low interface cost
4. High local preference

Correct Answer: 2

Explanation:

Packet Loss Priority, or PLP, provides an indication of how suitable traffic is for dropping when congestion occurs. Traffic marked with a higher loss priority can be treated as more eligible for packet loss compared with traffic assigned a lower loss priority. This allows a network to protect more important traffic during periods when queues become congested. PLP can work together with forwarding classes, schedulers, and drop profiles to create differentiated congestion behavior. It is not a routing metric like OSPF cost or BGP local preference. Proper PLP classification is particularly useful when applications have different requirements for reliability and delay.

Question 220:

Which Junos command can be used to examine the current OSPF link-state database?

1. show ospf database
2. show bgp summary
3. show arp
4. show lldp neighbors

Correct Answer: 1

Explanation:

The show ospf database command displays information from the OSPF Link-State Database. It is useful for examining the LSAs that the router has learned and for understanding how OSPF currently represents the network topology. During troubleshooting, administrators can use the command to verify whether expected LSAs are present and whether topology information appears consistent. The LSDB is the primary source of information used by the OSPF SPF calculation. If an expected network or router is missing from the database, further investigation may involve neighbor relationships, area configuration, LSA flooding, or interface status. The other listed commands provide information about different protocols or network functions.