View Full Juniper JN0-650 Exam Dumps and Practice Test Dumps.

 

Question 21:

Which protocol is used to dynamically exchange routing information between autonomous systems?

1. OSPF
2. IS-IS
3. BGP
4. RIP

Correct Answer: 3

Explanation:

Border Gateway Protocol (BGP) is the primary routing protocol used to exchange routing information between autonomous systems. BGP is classified as a path-vector routing protocol and makes routing decisions using attributes such as AS path, local preference, MED, and communities. It is commonly used between service providers, enterprises, and Internet peers. OSPF and IS-IS are primarily interior gateway protocols designed for routing within an autonomous system. RIP is also an interior routing protocol but is much less suitable for modern large-scale networks because of its limited scalability and slower convergence.

Question 22:

What is the primary purpose of the OSPF router ID?

1. To uniquely identify an OSPF router
2. To determine the router’s MAC address
3. To assign an IP address to an interface
4. To select the default gateway

Correct Answer: 1

Explanation:

The OSPF router ID uniquely identifies a router within the OSPF routing domain. It is represented as a 32-bit value in IPv4 dotted-decimal format, although it does not have to correspond to an actual interface address. The router ID is used in OSPF neighbor relationships, LSAs, and the DR/BDR election process. A stable router ID is important for predictable OSPF operation. It does not assign interface addresses or determine MAC addresses. Administrators can explicitly configure the router ID in Junos to avoid unexpected changes caused by interface state changes.

Question 23:

Which command is commonly used on a Junos device to display detailed information about OSPF neighbors?

1. show bgp summary
2. show ospf neighbor
3. show route forwarding-table
4. show interfaces extensive

Correct Answer: 2

Explanation:

The show ospf neighbor command displays information about OSPF neighbors and their adjacency states. It can help administrators verify whether OSPF peers have successfully established communication and determine their current states. Information such as the neighbor router ID, interface, state, and adjacency details can be useful when troubleshooting routing problems. show bgp summary is intended for BGP sessions, while show route forwarding-table focuses on forwarding information. Interface commands provide physical and logical interface details but do not directly provide the OSPF neighbor database.

Question 24:

Which routing protocol uses the SPF algorithm to calculate shortest paths through the network?

1. BGP
2. RIP
3. OSPF
4. DHCP

Correct Answer: 3

Explanation:

OSPF is a link-state routing protocol that uses the Shortest Path First (SPF) algorithm to calculate optimal paths through the network. Each OSPF router maintains a link-state database representing the topology of its area. When topology changes occur, OSPF can recalculate routes based on the updated information. BGP uses a path-vector approach and selects routes based on multiple attributes. RIP uses a distance-vector mechanism based primarily on hop count. DHCP is not a routing protocol at all; it is used to provide network configuration information such as IP addresses.

Question 25:

Which BGP session type is normally established between routers in the same autonomous system?

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

Correct Answer: 2

Explanation:

Internal BGP, or iBGP, is used to exchange BGP routing information between BGP speakers that belong to the same autonomous system. External BGP, or eBGP, is normally used between routers belonging to different autonomous systems. iBGP is important in large enterprise and service-provider networks because it allows BGP routes learned from external peers to be distributed internally. iBGP has specific rules concerning route propagation, including the traditional requirement that routes learned from one iBGP peer are not advertised to another iBGP peer unless mechanisms such as route reflection are used.

Question 26:

Which BGP feature reduces the need for a full mesh of iBGP sessions?

1. Route reflector
2. DHCP relay
3. VRRP
4. LACP

Correct Answer: 1

Explanation:

A BGP route reflector reduces the need for a full mesh of iBGP sessions. In a traditional iBGP design, every BGP router may need to establish a session with every other BGP router, which becomes difficult to scale as the number of routers increases. A route reflector can receive routes from clients and reflect selected routes to other clients. This significantly reduces the number of required sessions. DHCP relay forwards DHCP messages between networks, VRRP provides gateway redundancy, and LACP manages link aggregation. Route reflection is therefore an important BGP scalability mechanism.

Question 27:

Which Junos command displays the current configuration hierarchy in a human-readable form?

1. show route
2. show interfaces terse
3. show configuration
4. show system uptime

Correct Answer: 3

Explanation:

The show configuration command displays the Junos configuration in hierarchical format. It is commonly used in configuration mode or operational mode to inspect configured statements and verify whether required settings are present. Junos separates configuration from operational commands, allowing administrators to review and modify configuration before committing changes. show route displays routing information, show interfaces terse provides a concise interface status summary, and show system uptime displays system uptime information. Reviewing the configuration is an essential step when troubleshooting incorrect routing, interface, security, or service settings.

Question 28:

Which Junos command is commonly used to display a concise summary of interface status?

1. show interfaces terse
2. show route
3. show ospf database
4. show system processes

Correct Answer: 1

Explanation:

The show interfaces terse command provides a concise summary of interface information, including interface names, administrative state, link state, and protocol status. It is one of the most frequently used commands for quickly determining whether physical and logical interfaces are operational. More detailed information can be obtained using commands such as show interfaces extensive. Routing commands focus on Layer 3 route information, while OSPF database commands display routing protocol information. When troubleshooting connectivity, checking interface status is often one of the first diagnostic steps.

Question 29:

Which technology provides first-hop gateway redundancy by allowing multiple routers to share a virtual IP address?

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

Correct Answer: 2

Explanation:

Virtual Router Redundancy Protocol (VRRP) provides first-hop redundancy by allowing multiple routers to participate in a virtual router group. The routers share a virtual IP address that hosts can use as their default gateway. One router typically operates as the master while another can take over if the master fails. This provides improved gateway availability without requiring hosts to change their configured default gateway. LACP is used for link aggregation, LDP distributes MPLS labels, and LLDP provides neighbor discovery information. VRRP is therefore appropriate for gateway redundancy.

Question 30:

What is the main purpose of LACP in a Junos network?

1. Exchange BGP routes
2. Create an aggregate Ethernet interface from multiple physical links
3. Distribute MPLS labels
4. Discover neighboring devices

Correct Answer: 2

Explanation:

The Link Aggregation Control Protocol (LACP) allows multiple physical Ethernet links to operate together as a logical aggregated interface. In Junos, this is commonly implemented using an aggregated Ethernet interface. Link aggregation can increase available bandwidth and provide redundancy because traffic can continue using remaining links if one physical member fails. LACP also helps dynamically negotiate and maintain the link aggregation relationship between compatible devices. BGP handles routing information, LDP distributes MPLS labels, and LLDP performs neighbor discovery. LACP is therefore useful for improving both capacity and resiliency.

Question 31:

Which protocol is commonly used to exchange link-state routing information in large service-provider networks?

1. DHCP
2. IS-IS
3. VRRP
4. LACP

Correct Answer: 2

Explanation:

IS-IS is a link-state interior gateway protocol widely used in large service-provider networks. Like OSPF, it builds a link-state database and uses the SPF algorithm to calculate paths. IS-IS is highly scalable and supports hierarchical routing through different levels, making it suitable for large infrastructures. DHCP provides host configuration, VRRP provides first-hop redundancy, and LACP provides link aggregation. In Junos environments, IS-IS can be deployed as the IGP underneath technologies such as MPLS and traffic engineering. Its scalability and operational characteristics make it popular among service providers.

Question 32:

Which MPLS label operation removes the top label from an MPLS packet?

1. Push
2. Swap
3. Pop
4. Rewrite

Correct Answer: 3

Explanation:

The MPLS pop operation removes the top label from an MPLS packet. This commonly occurs when the packet reaches a router that no longer needs the MPLS label for forwarding. A push operation adds a label to a packet, while swap replaces an existing label with another label. MPLS forwarding relies on these label operations to move packets through label-switched paths. Understanding push, swap, and pop operations is important when troubleshooting MPLS forwarding behavior. Junos operational commands can be used to inspect labels and verify whether expected MPLS forwarding entries exist.

Question 33:

Which Junos feature allows administrators to filter or control packets based on fields such as source address, destination address, and protocol?

1. Firewall filter
2. Routing policy
3. Routing instance
4. Scheduler

Correct Answer: 1

Explanation:

Junos firewall filters provide packet-filtering capabilities based on match conditions such as source address, destination address, protocol, ports, and other packet fields. Actions can include accepting, discarding, counting, logging, or modifying traffic characteristics depending on the filter and platform. Firewall filters can be applied at appropriate interface locations to control traffic. Routing policies operate on routing information rather than individual packets, routing instances provide routing separation, and schedulers control traffic transmission. Firewall filters are therefore a fundamental tool for packet-level traffic control and protection.

Question 34:

Which BGP attribute is generally preferred when its value is higher during route selection?

1. MED
2. Local preference
3. AS path length
4. IGP metric

Correct Answer: 2

Explanation:

BGP generally prefers a higher Local Preference value when comparing otherwise suitable routes. Local preference is an internal BGP attribute used to influence the preferred exit point from an autonomous system. It is propagated among iBGP peers and allows an organization to establish consistent outbound routing decisions. MED, by comparison, is generally preferred when lower. AS path selection generally favors a shorter path, while IGP metrics can influence selection later in the BGP decision process. Proper use of local preference is an important method for controlling outbound traffic across multiple external connections.

Question 35:

Which Junos mechanism can prevent unauthorized devices from establishing Layer 2 connectivity on an access port?

1. Port security
2. Route reflection
3. MPLS LDP
4. OSPF authentication

Correct Answer: 1

Explanation:

Port security mechanisms can help restrict which devices are permitted to use a Layer 2 access port. Depending on the Junos platform and configuration, administrators can control MAC addresses or take actions when unexpected devices appear. This helps reduce unauthorized network access at the access layer. Route reflection is a BGP scalability mechanism, LDP distributes MPLS labels, and OSPF authentication protects routing protocol communication rather than controlling Layer 2 endpoint access. Port-level security should be combined with broader authentication and access-control mechanisms when stronger endpoint security is required.

Question 36:

Which protocol is used to negotiate the active and standby roles in a redundant gateway configuration?

1. OSPF
2. BGP
3. VRRP
4. IS-IS

Correct Answer: 3

Explanation:

VRRP is designed to provide redundant default gateway functionality. Multiple routers participate in a virtual router group, and one router assumes the master role while other routers remain available to take over if needed. Hosts use the shared virtual IP address rather than depending on the physical address of one router. This makes gateway failure less disruptive to end devices. OSPF, BGP, and IS-IS are routing protocols and do not provide the same first-hop gateway redundancy function. VRRP is therefore the appropriate technology when high availability is required for a default gateway.

Question 37:

What is the primary purpose of an MPLS label-switched path (LSP)?

1. Provide a path for forwarding MPLS-labeled traffic
2. Assign IP addresses to endpoints
3. Discover Layer 2 neighbors
4. Encrypt Ethernet frames

Correct Answer: 1

Explanation:

An MPLS Label-Switched Path (LSP) represents a forwarding path through an MPLS network. Packets entering the MPLS domain can receive labels and then be forwarded through the network based on label operations rather than performing a complete IP lookup at every hop. LSPs are fundamental to MPLS services and can support applications such as Layer 3 VPNs and traffic engineering. MPLS itself does not assign endpoint IP addresses, provide Layer 2 neighbor discovery, or inherently encrypt Ethernet frames. Correct LSP operation depends on proper routing and label-distribution configuration.

Question 38:

Which command can be used to verify BGP peer session status on a Junos device?

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

Correct Answer: 3

Explanation:

The show bgp summary command provides a concise overview of BGP peer sessions and their current status. It can show information such as the peer address, autonomous system, state, and number of received prefixes. This makes it a valuable first step when troubleshooting BGP connectivity or route exchange. show ospf neighbor is used for OSPF adjacencies, show lldp neighbors displays directly connected neighbor information, and show ethernet-switching table displays Layer 2 MAC learning information. Administrators can use more detailed BGP commands after identifying an issue with a peer.

Question 39:

Which Ethernet switching table entry associates a learned MAC address with a switch interface?

1. ARP entry
2. MAC forwarding entry
3. BGP route
4. OSPF LSA

Correct Answer: 2

Explanation:

A MAC forwarding entry associates a learned Layer 2 MAC address with the interface through which the device was learned. Ethernet switches use this information to forward frames toward the correct destination instead of flooding them out all ports. The MAC address table is populated through mechanisms such as source MAC learning. ARP entries associate IPv4 addresses with MAC addresses, while BGP routes and OSPF LSAs contain Layer 3 routing information. When troubleshooting Layer 2 connectivity, examining the MAC forwarding table can help determine whether the switch has correctly learned an endpoint.

Question 40:

Which Junos configuration command is used to apply candidate configuration changes and make them active?

1. rollback
2. commit
3. deactivate
4. exit

Correct Answer: 2

Explanation:

The commit command activates the candidate configuration in Junos. Junos uses a commit-based configuration model, allowing administrators to make multiple changes and review them before applying them to the active configuration. This provides greater control and reduces the risk of accidentally applying incomplete changes. The rollback command can be used to return toward a previous configuration, while deactivate disables configuration statements without deleting them. The exit command leaves the current configuration hierarchy. Administrators should review changes carefully before committing, especially on production network devices.