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Question 1:

Which routing protocol is commonly used as an Interior Gateway Protocol (IGP) in a Junos enterprise network?

1. BGP
2. OSPF
3. LDP
4. EVPN

Correct Answer: 2

Explanation:

OSPF is an Interior Gateway Protocol designed to exchange routing information within a single autonomous system. It uses a link-state database and the Shortest Path First (SPF) algorithm to calculate the best paths. In Junos enterprise networks, OSPF is commonly used for internal routing because it converges quickly and supports hierarchical designs through areas. BGP is generally used for inter-domain routing, while LDP is primarily associated with MPLS label distribution. EVPN is a control-plane technology commonly used with VXLAN and other Layer 2/Layer 3 services.

Question 2:

Which OSPF router is elected on a broadcast network to reduce the number of adjacencies required between routers?

1. Area Border Router
2. Autonomous System Boundary Router
3. Designated Router
4. Internal Router

Correct Answer: 3

Explanation:

On broadcast multiaccess networks such as Ethernet, OSPF elects a Designated Router (DR) and a Backup Designated Router (BDR). The DR reduces the number of full OSPF adjacencies required because routers primarily establish full adjacencies with the DR and BDR rather than with every other router. The DR also helps coordinate the exchange of link-state information. The election is based on OSPF interface priority and router ID. An Area Border Router connects different OSPF areas, while an ASBR connects OSPF to another routing domain.

Question 3:

Which BGP attribute is primarily used to influence the outbound path selection from an autonomous system?

1. MED
2. Local preference
3. Origin
4. AS path

Correct Answer: 2

Explanation:

The BGP Local Preference attribute is used within an autonomous system to influence which exit path should be preferred for outbound traffic. A higher local preference value is preferred. Because it is propagated throughout the AS, it allows network administrators to consistently influence outbound routing decisions. MED is generally used to suggest an inbound path to a neighboring autonomous system, while AS path length is another BGP selection factor. The Origin attribute indicates how a route was introduced into BGP. Understanding these attributes is essential when designing and troubleshooting enterprise BGP policies.

Question 4:

Which Junos feature allows an administrator to modify route attributes before routes are installed into the routing table?

1. Routing policy
2. Firewall filter
3. CoS scheduler
4. SNMP

Correct Answer: 1

Explanation:

Junos routing policies provide granular control over route import, export, acceptance, rejection, and attribute modification. A policy can match routes based on criteria such as prefix, protocol, community, or AS path and then perform actions such as modifying local preference, MED, communities, or next-hop information. Routing policies are commonly applied to protocols such as BGP, OSPF, and other routing processes. Firewall filters operate on packets rather than routing information, while CoS schedulers control traffic transmission behavior. SNMP is primarily used for network monitoring and management.

Question 5:

Which BGP attribute contains the sequence of autonomous systems through which a route has passed?

1. Local preference
2. MED
3. Community
4. AS path

Correct Answer: 4

Explanation:

The AS path attribute records the autonomous systems that a BGP route has traversed. BGP uses this attribute both for loop prevention and as part of its route-selection process. When a route is advertised to another autonomous system, the advertising router normally adds its own AS number to the AS path. If a router receives a route containing its own AS number, it can reject the route to prevent routing loops. A shorter AS path is generally preferred when comparing otherwise similar routes. Local preference, MED, and communities serve different purposes in BGP policy.

Question 6:

Which Junos CoS component determines how packets are grouped for queueing and scheduling?

1. Forwarding class
2. Route target
3. Routing instance
4. Security zone

Correct Answer: 1

Explanation:

A forwarding class identifies a class of traffic that should receive specific treatment within the Junos Class of Service framework. Packets can be classified based on fields such as DSCP or 802.1p, and the resulting classification can map traffic into forwarding classes. Forwarding classes are then associated with queues and schedulers that determine how traffic is transmitted during congestion. Route targets are used with VPN routing, routing instances provide traffic separation or specialized routing environments, and security zones are associated with firewall security policies.

Question 7:

Which CoS mechanism is specifically designed to limit the rate of traffic entering or passing through a device?

1. Scheduler
2. Policier
3. Rewrite rule
4. Forwarding class

Correct Answer: 2

Explanation:

A policer limits traffic to a configured rate and can take actions when traffic exceeds the allowed rate. It is commonly used to control bandwidth consumption and protect network resources. Depending on configuration, excess traffic can be dropped or otherwise marked. A scheduler controls how packets are transmitted from queues, while a forwarding class categorizes traffic for treatment by the CoS system. Rewrite rules modify packet markings, such as DSCP or 802.1p values. Policers are therefore particularly useful when an administrator needs to enforce bandwidth limits.

Question 8:

Which EVPN route type advertises MAC addresses and associated IP information for a host?

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 the MAC/IP Advertisement route. It is used to advertise endpoint MAC addresses and, when applicable, their associated IP addresses through the EVPN control plane. This allows remote devices to learn endpoint reachability without relying solely on traditional data-plane MAC learning. Route Type 1 is associated with Ethernet Auto-Discovery, while Route Type 3 is an Inclusive Multicast Ethernet Tag route. Route Type 5 is used for IP prefix advertisement. Understanding these route types is important when troubleshooting EVPN-VXLAN forwarding behavior.

Question 9:

What is the primary purpose of VXLAN in a modern data center network?

1. Encrypting routing updates
2. Replacing BGP
3. Providing Layer 2 overlay connectivity across a Layer 3 network
4. Assigning IP addresses to hosts

Correct Answer: 3

Explanation:

VXLAN provides an overlay mechanism that can extend Layer 2 segments across an underlying Layer 3 IP network. It encapsulates Ethernet frames inside UDP packets, allowing organizations to build scalable virtual networks over an IP-based underlay. VXLAN is frequently combined with EVPN, where BGP EVPN provides control-plane signaling for endpoint information. VXLAN itself does not replace BGP, assign host IP addresses, or inherently encrypt routing updates. Its major benefit is the ability to provide scalable network virtualization while allowing the physical infrastructure to operate as a routed IP fabric.

Question 10:

Which protocol is commonly used by Junos devices to distribute MPLS labels in an IGP-based MPLS network?

1. LDP
2. DHCP
3. LLDP
4. VRRP

Correct Answer: 1

Explanation:

Label Distribution Protocol (LDP) is commonly used to distribute MPLS labels between routers. It works with an underlying IGP, such as OSPF or IS-IS, to establish label-switched paths based on the IP routing topology. LDP allows routers to associate labels with forwarding equivalence classes and exchange those labels with neighboring LDP peers. DHCP provides address configuration, LLDP discovers directly connected devices, and VRRP provides first-hop redundancy. In MPLS environments, troubleshooting often requires verifying both the IGP routing state and LDP session and label information.

Question 11:

Which OSPF area type is designed to reduce the amount of external routing information carried within an area?

1. Backbone area
2. Stub area
3. Transit area
4. Core area

Correct Answer: 2

Explanation:

A stub area is an OSPF area designed to reduce the amount of external routing information that must be maintained within the area. Instead of receiving individual external routes, routers inside a stub area can use a default route toward the appropriate exit point. This can reduce routing table size and simplify routing information within the area. The backbone area is Area 0 and provides inter-area connectivity. The terms transit area and core area do not describe the specific OSPF area type intended to suppress external route information.

Question 12:

Which BGP attribute is commonly used to provide a hint to an external neighboring AS about the preferred inbound path?

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

Correct Answer: 3

Explanation:

The Multi-Exit Discriminator (MED) is a BGP attribute used to influence how a neighboring autonomous system selects among multiple entry points into the advertising AS. Generally, a lower MED is preferred when comparing routes from the same neighboring AS, subject to the applicable BGP selection rules. MED is therefore commonly used to communicate an inbound path preference. Local preference is primarily used internally to influence outbound traffic. Origin identifies the source type of a BGP route, while Weight is a vendor-specific attribute and is not propagated between BGP autonomous systems.

Question 13:

Which Junos feature is used to apply different routing tables and forwarding behavior to logically separated network environments?

1. Routing instance
2. Scheduler
3. Firewall filter
4. Forwarding class

Correct Answer: 1

Explanation:

Routing instances provide logical separation of routing information and forwarding behavior on Junos devices. They are commonly used to implement services such as virtual routing and forwarding (VRF), where multiple customers or network environments can maintain separate routing tables on the same physical device. Each routing instance can have its own interfaces, routes, and routing protocols, depending on the configuration. Forwarding classes and schedulers belong to Class of Service, while firewall filters control packet handling based on configured match conditions and actions. Routing instances are therefore important for network segmentation and multitenancy.

Question 14:

In an EVPN multihoming deployment, what is the main purpose of an Ethernet Segment Identifier (ESI)?

1. Identify an OSPF area
2. Identify a shared Ethernet segment connected to multiple devices
3. Identify an MPLS label
4. Identify a BGP autonomous system

Correct Answer: 2

Explanation:

An Ethernet Segment Identifier (ESI) identifies an Ethernet segment that is connected to multiple EVPN Provider Edge devices. It is an important component of EVPN multihoming because it allows the network to represent the shared segment consistently across participating devices. ESI information supports mechanisms such as multihoming, redundancy, and designated forwarder election. An ESI does not identify an OSPF area, MPLS label, or BGP autonomous system. Proper ESI configuration is particularly important when implementing redundant connections between customer equipment and multiple EVPN devices.

Question 15:

Which Junos operational command is commonly used to display the routing table?

1. show interfaces terse
2. show route
3. show chassis hardware
4. show configuration

Correct Answer: 2

Explanation:

The show route operational command displays routing information from the Junos routing tables. It can be used to inspect routes learned through protocols such as OSPF, BGP, IS-IS, or static configuration. Administrators can also use additional options to examine specific routes, protocols, or routing tables. show interfaces terse provides interface status information, show chassis hardware displays hardware details, and show configuration displays the candidate or committed configuration depending on context. During routing troubleshooting, show route is one of the fundamental commands for determining whether the expected routes are present.

Question 16:

Which BGP mechanism can be used to group routes so that routing policies can be applied to them as a set?

1. Communities
2. Router ID
3. Next-hop self
4. Keepalive

Correct Answer: 1

Explanation:

BGP communities are attributes that allow routes to be logically grouped and tagged with policy information. Administrators can then create routing policies that match specific communities and apply actions to all routes carrying those tags. This makes communities extremely useful for scalable BGP policy design. For example, an organization can use communities to identify routes that should receive a particular local preference or should be advertised to specific peers. Router ID identifies a BGP speaker, next-hop self changes next-hop behavior, and keepalive messages help maintain the BGP session.

Question 17:

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

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

Correct Answer: 3

Explanation:

EVPN Route Type 3 is the Inclusive Multicast Ethernet Tag route. It is used to advertise information required for handling broadcast, unknown unicast, and multicast traffic within an EVPN service. This route type can help build the necessary replication or forwarding information between participating EVPN devices. Route Type 1 is associated with Ethernet Auto-Discovery, Route Type 2 advertises MAC/IP information, and Route Type 5 advertises IP prefixes. Understanding EVPN route types is essential for diagnosing control-plane learning and traffic-forwarding issues in EVPN-based networks.

Question 18:

Which protocol provides neighbor discovery information such as device identity, port information, and capabilities on directly connected links?

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

Correct Answer: 3

Explanation:

The Link Layer Discovery Protocol (LLDP) allows directly connected network devices to exchange information about themselves. This can include system identity, interface or port information, capabilities, and other management details. LLDP is particularly useful for network discovery and troubleshooting because administrators can determine what device is connected to a specific interface. OSPF and BGP are routing protocols that exchange network reachability information, while LACP is used to negotiate and maintain link aggregation. LLDP operates at the data-link layer and is independent of IP routing.

Question 19:

Which OSPF database contains the link-state information used by the SPF algorithm?

1. ARP table
2. MAC table
3. Forwarding table
4. Link-state database

Correct Answer: 4

Explanation:

OSPF maintains a Link-State Database (LSDB) containing the link-state information received through OSPF Link-State Advertisements. Each router uses this information to build a representation of the topology within its OSPF area. The Shortest Path First algorithm then processes the LSDB to calculate the best paths and populate the routing table. The ARP table maps IP addresses to MAC addresses, the MAC table contains Layer 2 forwarding information, and the forwarding table contains information used to forward packets. The LSDB is therefore central to OSPF path calculation.

Question 20:

Which Junos feature can be used to prioritize delay-sensitive traffic such as voice by assigning it to a dedicated queue with appropriate scheduling?

1. Class of Service
2. Routing policy
3. Routing instance
4. ARP

Correct Answer: 1

Explanation:

Junos Class of Service (CoS) provides mechanisms for classifying and prioritizing traffic according to application or service requirements. Voice traffic is often delay-sensitive and can be placed into an appropriate forwarding class and queue. A scheduler can then provide suitable bandwidth and priority characteristics to that traffic. This helps reduce the impact of congestion and packet loss on real-time applications. Routing policies control route information, routing instances provide logical routing separation, and ARP resolves IPv4 addresses to Layer 2 addresses. CoS is therefore the appropriate feature for differentiated traffic treatment.