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Question 101:

Which OSPFv3 feature allows a router to establish an adjacency with another router over an IPv6-enabled interface?

1. IPv6 link-local addressing
2. IPv4 loopback addressing
3. BGP next-hop resolution
4. MPLS label distribution

Correct Answer: 1

Explanation:

OSPFv3 is designed specifically to support IPv6 routing. OSPFv3 uses IPv6 link-local addresses for neighbor discovery and adjacency formation. These addresses are automatically configured on IPv6-enabled interfaces and remain valid only on the local link. OSPFv3 packets use IPv6 as their transport, and routers use link-local addresses as the next-hop information for many OSPFv3 operations. This differs from OSPFv2, which operates over IPv4. Understanding the role of link-local addressing is important when troubleshooting OSPFv3 neighbor relationships because an incorrect or missing IPv6 configuration can prevent adjacency establishment even when the physical interface is operational.

Question 102:

Which Junos command is most useful for verifying the current OSPF neighbor relationships?

1. show bgp summary
2. show ospf neighbor
3. show ethernet-switching table
4. show lldp neighbors

Correct Answer: 2

Explanation:

The show ospf neighbor command displays information about OSPF neighbor relationships on the router. It can be used to determine whether configured OSPF neighbors have successfully formed adjacencies and to inspect their current states. Important information can include the neighbor router ID, interface, state, and related timing information. This command is particularly useful during troubleshooting when routes are missing from the routing table. If an expected neighbor does not appear, the administrator can investigate issues such as area mismatches, authentication problems, interface configuration, network type, or hello and dead interval differences. Operational verification is an important part of maintaining stable OSPF deployments.

Question 103:

In BGP, which attribute is normally used to prefer one exit path over another within an autonomous system?

1. MED
2. Origin
3. Local preference
4. Community

Correct Answer: 3

Explanation:

BGP local preference is commonly used to influence outbound path selection within an autonomous system. A higher local preference value is preferred, making it useful for selecting the preferred exit point for traffic leaving the AS. Because local preference is propagated through iBGP, it can influence path selection across multiple routers within the same autonomous system. Network administrators often configure routing policies to assign different local preference values based on the destination prefix, upstream provider, or other routing requirements. This provides a controlled way to select preferred external paths while maintaining consistent routing decisions throughout the internal BGP topology.

Question 104:

Which BGP attribute is primarily intended to provide information about the preferred entry point into an autonomous system?

1. MED
2. Local preference
3. AS path
4. Next hop

Correct Answer: 1

Explanation:

The Multi-Exit Discriminator, or MED, is a BGP attribute used to provide neighboring autonomous systems with information about preferred entry points. When multiple links exist between two autonomous systems, an administrator can use MED to indicate which connection should be preferred for incoming traffic. In general, a lower MED is preferred when comparing otherwise eligible routes from the same neighboring AS. MED is commonly manipulated through routing policies. Because BGP route selection involves several attributes and implementation details, MED should not be considered in isolation. Proper policy design is important when using MED to influence inbound traffic engineering.

Question 105:

What is the primary purpose of LLDP-MED in an enterprise network?

1. Distributing BGP routes between switches
2. Providing device discovery and endpoint information for media devices
3. Establishing MPLS LSPs
4. Encrypting voice traffic

Correct Answer: 2

Explanation:

LLDP-MED extends the capabilities of the Link Layer Discovery Protocol for environments containing media endpoints such as IP phones. It can provide information useful for device discovery, network policy, location identification, and voice-related deployment. In enterprise networks, LLDP-MED can help an IP phone learn network-related information and allows network administrators to identify connected devices more effectively. It works at the link layer and does not provide encryption or routing functionality. When deploying IP telephony, LLDP-MED can work alongside features such as voice VLANs and Power over Ethernet to simplify endpoint provisioning and improve operational visibility.

Question 106:

Which Junos feature provides electrical power to compatible Ethernet-connected devices such as IP phones and access points?

1. LLDP
2. CoS
3. PoE
4. EVPN

Correct Answer: 3

Explanation:

Power over Ethernet, or PoE, allows compatible network devices to receive electrical power through their Ethernet connection. Common PoE-powered devices include IP phones, wireless access points, and certain security or IoT devices. This reduces the need for separate electrical power connections at each endpoint and simplifies deployment. On supported Junos platforms, administrators can configure and monitor PoE-related settings to control how power is supplied to connected devices. PoE itself is separate from protocols such as LLDP, although LLDP or LLDP-MED can provide additional endpoint information in some deployments. Understanding both features is useful when troubleshooting IP phone connectivity and power issues.

Question 107:

In a Junos Class of Service configuration, what is the primary purpose of a forwarding class?

1. To identify a group of packets for specific forwarding treatment
2. To establish an OSPF adjacency
3. To assign an IP address to an interface
4. To authenticate network users

Correct Answer: 1

Explanation:

A forwarding class identifies traffic that should receive a particular forwarding treatment within a Junos CoS implementation. Traffic can be classified according to characteristics such as interface, VLAN, packet markings, or other classification criteria, and then assigned to forwarding classes. These classes can subsequently be associated with scheduling and queueing behavior. For example, voice traffic can be placed into a forwarding class designed to provide low latency and appropriate queue treatment. Forwarding classes are therefore an important part of traffic differentiation and congestion management. They do not perform routing, authentication, or interface addressing functions.

Question 108:

What is the purpose of a CoS scheduler in Junos?

1. To calculate OSPF shortest paths
2. To control how queued traffic receives transmission resources
3. To establish BGP sessions
4. To assign MAC addresses

Correct Answer: 2

Explanation:

A CoS scheduler controls how traffic in output queues is transmitted when multiple traffic classes compete for available interface bandwidth. Scheduling mechanisms can determine characteristics such as transmission priority and bandwidth allocation among different queues. This is especially important during congestion because the scheduler determines which traffic receives service and how available resources are distributed. For example, delay-sensitive voice traffic may require more favorable treatment than ordinary data traffic. Schedulers work together with forwarding classes, queues, classifiers, and other CoS components to implement an overall quality-of-service strategy. They do not participate in routing protocol calculations or BGP session establishment.

Question 109:

Which EVPN route type advertises MAC address and IP address information associated with a MAC/IP binding?

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

Correct Answer: 2

Explanation:

EVPN route type 2 is commonly used to advertise MAC and IP address information associated with an endpoint. This allows participating EVPN devices to distribute reachability information for MAC addresses and, when available, their corresponding IP addresses. The information can be used for Ethernet VPN forwarding and integrated routing and bridging scenarios. Route type 1 is associated with Ethernet Auto-Discovery information, while route type 3 is used for inclusive multicast Ethernet traffic distribution. Understanding the different EVPN route types is important when troubleshooting EVPN control-plane learning and determining why a particular endpoint is or is not reachable across an EVPN fabric.

Question 110:

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

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

Correct Answer: 1

Explanation:

EVPN route type 3 is known as the Inclusive Multicast Ethernet Tag route. It provides information used to establish the required replication or tunnel-related behavior for forwarding broadcast, unknown unicast, and multicast traffic across an EVPN network. This is particularly relevant in VXLAN-based EVPN fabrics where VTEPs need control-plane information about how to reach other VTEPs for a given Ethernet segment or VNI. Route type 3 complements other EVPN route types that advertise endpoint reachability or multihoming information. Correctly identifying route types is essential when troubleshooting EVPN control-plane behavior and understanding how different traffic categories are distributed across the fabric.

Question 111:

What is the primary purpose of an Ethernet Segment Identifier (ESI) in EVPN?

1. Identifying an OSPF area
2. Identifying an Ethernet segment connected to multiple PE devices
3. Identifying a BGP autonomous system
4. Identifying a VXLAN packet header

Correct Answer: 2

Explanation:

An Ethernet Segment Identifier, or ESI, identifies an Ethernet segment that can be connected to multiple provider edge devices in an EVPN deployment. ESI is especially important for EVPN multihoming because multiple PE devices can provide connectivity to the same customer-side Ethernet segment. The EVPN control plane uses ESI-related information to coordinate forwarding behavior and prevent undesirable loops. It also supports multihoming capabilities such as redundancy and traffic distribution. ESI is not an OSPF area identifier, BGP autonomous system identifier, or VXLAN header field. Understanding ESI is fundamental when designing and troubleshooting EVPN multihoming environments.

Question 112:

In an EVPN multihoming topology, what is the main purpose of Designated Forwarder election?

1. To determine which PE forwards certain BUM traffic toward a multihomed Ethernet segment
2. To select the BGP router ID
3. To calculate the OSPF shortest path
4. To assign VLAN IDs

Correct Answer: 1

Explanation:

Designated Forwarder, or DF, election is used in EVPN multihoming to determine which PE device should forward certain broadcast, unknown unicast, and multicast traffic toward a multihomed Ethernet segment. Without appropriate coordination, multiple PEs could forward the same traffic toward the customer segment, potentially creating duplicate frames or loops. DF election provides a mechanism for controlling this forwarding behavior. EVPN uses the Ethernet Segment Identifier and related control-plane information to support multihoming operations. DF election is therefore an important part of EVPN redundancy and loop prevention. It is not responsible for selecting BGP or OSPF paths.

Question 113:

What is the main purpose of a VXLAN Network Identifier (VNI)?

1. To identify an OSPF process
2. To identify a logical VXLAN segment
3. To identify a BGP peer
4. To identify a physical Ethernet port

Correct Answer: 2

Explanation:

A VXLAN Network Identifier, or VNI, identifies a logical Layer 2 segment within a VXLAN overlay network. It provides segmentation between different virtual networks while allowing those networks to extend across an IP-based transport infrastructure. VXLAN encapsulates Ethernet frames inside UDP/IP packets, allowing Layer 2 connectivity to be carried across a Layer 3 underlay. The VNI is carried within the VXLAN header and helps the receiving VTEP determine which logical network the traffic belongs to. This provides much greater segmentation scalability than relying solely on traditional VLAN identifiers in large data-center environments.

Question 114:

Which device function performs VXLAN encapsulation for traffic entering a VXLAN overlay?

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

Correct Answer: 1

Explanation:

A VXLAN Tunnel Endpoint, or VTEP, performs VXLAN encapsulation and decapsulation at the boundary of the VXLAN overlay. When a frame enters the overlay, the originating VTEP encapsulates the Ethernet frame inside a VXLAN/UDP/IP packet and sends it across the IP underlay toward the destination VTEP. The receiving VTEP removes the VXLAN encapsulation and forwards the original Ethernet frame toward the destination endpoint. VTEPs therefore connect the local network segments to the VXLAN overlay. They are a fundamental component of VXLAN-based EVPN architectures and allow Layer 2 segments to be transported across a routed IP infrastructure.

Question 115:

What is the primary purpose of MAC RADIUS authentication on an Ethernet access network?

1. To authenticate devices based on their MAC addresses through a RADIUS server
2. To establish OSPF adjacencies
3. To exchange EVPN routes
4. To assign MPLS labels

Correct Answer: 1

Explanation:

MAC RADIUS authentication allows a network device to authenticate an endpoint using its MAC address as the identity information sent toward a RADIUS authentication server. It is useful for devices that may not support traditional 802.1X authentication, such as certain printers, IoT devices, or specialized endpoints. The switch or access device communicates with the RADIUS server and can apply the authentication result to control network access. MAC-based authentication should be considered an access-control mechanism rather than a routing protocol. In enterprise environments, it can be combined with other authentication methods and appropriate policies to provide differentiated access for various endpoint types.

Question 116:

What is a common purpose of a guest VLAN in an access-control environment?

1. Providing restricted network access to unauthenticated or guest devices
2. Carrying only BGP control traffic
3. Transporting MPLS labels
4. Replacing the routing table

Correct Answer: 1

Explanation:

A guest VLAN can provide limited network connectivity to devices that do not successfully authenticate or that are intended to receive guest-level access. Instead of granting unrestricted access to the production network, the endpoint can be placed into a dedicated VLAN with appropriate restrictions. This approach is useful in enterprise access-control deployments where visitors or unknown devices require controlled connectivity. The guest VLAN can be combined with authentication and authorization mechanisms to determine when and how an endpoint is placed into the guest environment. Proper firewalling and access policies are still important because VLAN separation alone does not guarantee complete security.

Question 117:

What is the primary function of a CoS rewrite rule?

1. To change packet classification markings before traffic leaves an interface
2. To create an OSPF neighbor
3. To assign an IP address dynamically
4. To establish an EVPN multihoming relationship

Correct Answer: 1

Explanation:

A CoS rewrite rule changes selected packet header markings as traffic leaves a device. This can be useful when a network needs to communicate its internal forwarding-class treatment to another device using appropriate packet markings. Depending on the protocol and configuration, rewrite rules can modify fields such as IP precedence, DSCP, or IEEE 802.1p-related markings. This allows QoS information to be preserved or translated between different network domains. Rewrite rules are different from classifiers, which determine how incoming traffic should be classified. Together, classification and rewriting can provide consistent end-to-end traffic treatment across multiple network devices.

Question 118:

What does packet loss priority (PLP) indicate in a Junos CoS environment?

1. The likelihood that traffic can be dropped during congestion
2. The BGP autonomous system number
3. The OSPF router ID
4. The VLAN membership of a packet

Correct Answer: 1

Explanation:

Packet loss priority, or PLP, is a CoS-related marking used to indicate the relative importance of traffic when congestion occurs. Traffic with a higher loss priority is generally more suitable for dropping when resources become scarce. This allows the network to protect more important traffic while preferentially discarding less important packets during congestion. PLP can be assigned as part of classification or other CoS processing and can interact with drop profiles and queue management. It does not identify routing protocols, VLAN membership, or autonomous systems. Understanding PLP is useful when designing congestion-management policies for applications with different levels of traffic importance.

Question 119:

Which CoS mechanism is specifically used to limit the rate at which traffic is transmitted or accepted?

1. Classifier
2. Policer
3. Forwarding class
4. Rewrite rule

Correct Answer: 2

Explanation:

A policer controls traffic according to a configured rate and can take actions when traffic exceeds the defined limits. It is commonly used to enforce bandwidth policies, protect network resources, or control the amount of traffic entering a network. Depending on configuration, traffic that exceeds the permitted rate may be dropped or marked differently. A classifier, by contrast, determines how traffic should be categorized, while a forwarding class identifies the forwarding treatment. A rewrite rule changes packet markings, generally as traffic leaves an interface. Understanding these distinctions is important when building and troubleshooting Junos CoS configurations.

Question 120:

Which Junos operational command is most appropriate for examining the BGP routes learned by a router?

1. show ospf database
2. show ethernet-switching table
3. show route receive-protocol bgp
4. show lldp neighbors

Correct Answer: 3

Explanation:

The show route receive-protocol bgp command can be used to examine routes received from a specified BGP neighbor or BGP protocol instance. It is useful when troubleshooting BGP because it helps determine what routing information was received before or during the process of applying relevant routing policies. This can help distinguish between a problem with route reception and a problem caused by import policy or subsequent route selection. Other commands serve different purposes: OSPF database commands examine OSPF information, the Ethernet-switching table displays Layer 2 MAC learning, and LLDP commands show neighboring devices.