View Full Juniper JN0-637 Exam Dumps and Practice Test Dumps

 

Question 41. Which Junos command is used to display the current OSPF neighbor relationships?

1. show route protocol ospf
2. show ospf neighbor
3. show ospf database
4. show interfaces terse

Correct Answer: 2. show ospf neighbor

Explanation:
The show ospf neighbor command displays OSPF neighbor relationships established by a Junos device. It provides information such as the neighbor router ID, interface, address, state, and adjacency details. This command is especially useful when troubleshooting OSPF because it quickly shows whether expected neighbors have successfully formed adjacencies. OSPF neighbors may progress through states such as Init, 2-Way, ExStart, Exchange, Loading, and Full, depending on the network type and role. If an expected neighbor is missing or stuck in an intermediate state, administrators can investigate timers, area configuration, interface parameters, authentication, and connectivity.

Question 42. Which BGP session type is established between routers belonging to the same autonomous system?

1. eBGP
2. MP-BGP
3. iBGP
4. External OSPF

Correct Answer: 3. iBGP

Explanation:
Internal BGP, or iBGP, is used to exchange BGP routing information between BGP speakers within the same autonomous system. External BGP, or eBGP, is used between routers in different autonomous systems. iBGP is important because routes learned from external BGP peers may need to be distributed to other BGP speakers inside the local autonomous system. Traditional iBGP requires a full-mesh relationship between participating routers unless mechanisms such as route reflectors are used. Understanding the distinction between iBGP and eBGP is fundamental to designing and troubleshooting BGP-based networks.

Question 43. What is the primary purpose of a Junos routing-instance of type virtual-router?

1. To provide separate routing tables within the same device
2. To establish MPLS labels automatically
3. To replace the physical interfaces
4. To disable all routing protocols

Correct Answer: 1. To provide separate routing tables within the same device

Explanation:
A virtual-router routing instance provides an independent routing table and routing context on a Junos device. It allows interfaces and routes to be logically separated from the main routing table without requiring a separate physical router. This can be useful when networks need isolated routing domains or when overlapping address spaces must be handled independently. Routing instances can be configured for different purposes, including virtual routing, Layer 3 VPN services, and other specialized functions. The exact behavior depends on the routing-instance type and associated configuration.

Question 44. Which OSPF router type connects an OSPF area to other OSPF areas?

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

Correct Answer: 4. Area Border Router

Explanation:
An Area Border Router (ABR) connects one OSPF area to another OSPF area. An ABR maintains link-state information for the areas to which it is connected and participates in the exchange of inter-area routing information. Area 0 is the backbone area, and other OSPF areas normally connect to it through ABRs. An Autonomous System Boundary Router (ASBR), by contrast, connects OSPF to external routing domains and can introduce external routes into OSPF. Correctly understanding ABR and ASBR roles is important when designing multi-area OSPF networks and troubleshooting inter-area route propagation.

Question 45. Which BGP attribute is commonly used to identify a set of routes for applying routing policy?

1. Router ID
2. Community
3. Next hop
4. Originator ID

Correct Answer: 2. Community

Explanation:
BGP communities provide a flexible method for tagging routes with additional information that can be used in routing policies. Administrators can classify groups of routes by assigning community values and then match those communities in import or export policies. This can simplify large-scale policy configuration because a policy can act on a group of routes sharing the same tag rather than requiring every prefix to be listed individually. Standard, well-known, and extended communities are available for different purposes. Communities are particularly useful in service-provider environments and complex BGP policy designs.

Question 46. Which protocol is commonly used by Junos devices to dynamically distribute MPLS labels for IP routes?

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

Correct Answer: 1. LDP

Explanation:
The Label Distribution Protocol (LDP) is commonly used to distribute MPLS label bindings for routes in an MPLS network. LDP establishes sessions between neighboring routers and exchanges label information associated with forwarding equivalence classes. Routers can then use the learned labels to forward MPLS packets along label-switched paths. LDP typically works alongside an IGP such as OSPF or IS-IS, which provides the underlying IP reachability. LDP is different from LLDP, which is a Layer 2 neighbor-discovery protocol, and from VRRP, which provides first-hop gateway redundancy.

Question 47. What is the main purpose of the Junos request support information command?

1. To change the active routing protocol
2. To establish an OSPF adjacency
3. To collect diagnostic information for troubleshooting
4. To modify firewall filter terms

Correct Answer: 3. To collect diagnostic information for troubleshooting

Explanation:
The request support information command gathers a broad set of operational and diagnostic information from a Junos device. It can be useful when investigating complex problems or preparing information for technical support. Depending on the platform and command options, the collected information may include system status, configuration-related details, interface information, routing information, logs, and other operational data. Because the command can produce a large amount of output, administrators typically use it when a comprehensive diagnostic snapshot is required rather than as a routine first troubleshooting command.

Question 48. Which BGP route attribute is normally considered when selecting among multiple routes after higher-priority attributes have been evaluated?

1. AS path length
2. Interface description
3. VLAN ID
4. Ethernet MAC address

Correct Answer: 1. AS path length

Explanation:
AS path length is an important factor in BGP route selection. When multiple otherwise eligible BGP routes are available, a shorter AS path can be preferred over a longer one, depending on the complete route-selection process and configured policies. The AS path also provides loop-prevention information because an autonomous system can reject routes containing its own AS number. BGP route selection involves multiple attributes and decision steps, including local preference, route origin, MED under applicable conditions, and other factors. Administrators should therefore consider the complete selection process rather than treating AS path length as the only criterion.

Question 49. What is the purpose of a Layer 3 VPN VRF in a Junos provider network?

1. To store MAC addresses for switching
2. To isolate customer routing information from other routing domains
3. To replace MPLS labels
4. To provide physical interface redundancy

Correct Answer: 2. To isolate customer routing information from other routing domains

Explanation:
A Virtual Routing and Forwarding instance (VRF) provides a separate routing and forwarding context for a particular customer or logical network. In an MPLS Layer 3 VPN environment, each customer VRF maintains its own routes, allowing different customers to use overlapping address spaces without necessarily interfering with one another. The provider can use route distinguishers, route targets, and MP-BGP to carry VPN routes between PE routers while preserving logical separation. VRFs are therefore a key component of multi-tenant Layer 3 VPN architectures and are central to service-provider routing designs.

Question 50. Which command can be used to examine the OSPF link-state database on a Junos device?

1. show ospf database
2. show route forwarding-table
3. show bgp summary
4. show interfaces terse

Correct Answer: 1. show ospf database

Explanation:
The show ospf database command displays information contained in the OSPF link-state database. The database contains Link-State Advertisements (LSAs) describing topology information within the OSPF domain. Examining the database can help administrators understand what topology information an OSPF router has learned and can be useful when troubleshooting missing routes, unexpected adjacencies, or topology inconsistencies. The command can also be used with additional options to focus on particular areas, interfaces, or LSA types. This differs from show route, which displays routes calculated or selected from routing information.

Question 51. Which Junos mechanism allows configuration changes to be checked before they are committed?

1. commit check
2. rollback 0
3. request system reboot
4. clear configuration

Correct Answer: 1. commit check

Explanation:
The commit check command validates the candidate configuration without activating it. It checks the configuration for syntax and other configuration consistency requirements and reports errors that must be corrected before a successful commit. This is useful when making complex changes because administrators can identify problems while the candidate configuration is still inactive. A successful commit check does not mean the configuration has been applied to the device; a normal commit is still required. Using validation before committing can reduce the risk of applying an invalid or incomplete configuration.

Question 52. Which technology provides first-hop gateway redundancy by allowing multiple routers to share a virtual IP address?

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

Correct Answer: 3. VRRP

Explanation:
Virtual Router Redundancy Protocol (VRRP) provides first-hop gateway redundancy by allowing multiple routers to participate in a virtual router. A virtual IP address is associated with the VRRP group, and one router acts as the master while another can take over if the master becomes unavailable. Hosts can use the virtual address as their default gateway without needing to know which physical router is currently forwarding traffic. VRRP is therefore useful for improving gateway availability. LACP serves link aggregation, LDP distributes MPLS labels, and LLDP provides Layer 2 neighbor discovery.

Question 53. In Junos OS, what is the purpose of a policy statement term’s from section?

1. It specifies the actions to perform on matching routes
2. It defines the conditions that a route must match
3. It commits the routing policy
4. It activates a BGP session

Correct Answer: 2. It defines the conditions that a route must match

Explanation:
In a Junos routing policy term, the from section defines the match conditions used to determine whether a route is processed by that term. Conditions can include prefixes, protocols, communities, route types, AS paths, or other supported route attributes. If the route matches the specified conditions, the actions in the corresponding then section are evaluated. This separation between matching criteria and actions makes Junos policies flexible and structured. For example, a policy can identify BGP routes from a particular prefix list in the from section and then modify or accept those routes in the then section.

Question 54. Which Junos command is commonly used to inspect the status of installed physical hardware?

1. show route
2. show chassis hardware
3. show policy
4. show ospf neighbor

Correct Answer: 2. show chassis hardware

Explanation:
The show chassis hardware command provides information about the physical hardware installed in a Juniper device. Depending on the platform, the output can include chassis components, line cards, Routing Engines, power supplies, fan modules, and other hardware elements. This command is useful when verifying installed components, checking hardware inventory, or troubleshooting hardware-related issues. It differs from operational commands that focus on routing, interfaces, or protocols. When investigating a physical hardware problem, administrators can combine this command with chassis alarms, environment information, and interface status commands to develop a more complete picture.

Question 55. Which OSPF router is responsible for reducing the number of full adjacencies on a broadcast network segment?

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

Correct Answer: 1. Designated Router

Explanation:
On broadcast multi-access networks, OSPF elects a Designated Router (DR) and a Backup Designated Router (BDR) to reduce the number of full adjacencies that would otherwise be required between all routers. Instead of every router forming a full adjacency with every other router, routers establish full relationships with the DR and BDR. The DR also plays an important role in generating network LSAs for the segment. The BDR provides backup functionality if the DR fails. OSPF DR and BDR elections are relevant on network types such as Ethernet where multiple OSPF routers share a common broadcast segment.

Question 56. What is the primary purpose of an export policy applied to a BGP neighbor?

1. To determine which routes are advertised to that neighbor
2. To calculate the shortest OSPF path
3. To establish the physical link
4. To assign VLAN IDs

Correct Answer: 1. To determine which routes are advertised to that neighbor

Explanation:
A BGP export policy controls which routes a Junos device advertises to a particular BGP neighbor and can also modify attributes before advertisement. The policy can match prefixes, communities, AS paths, protocols, and other route characteristics. Actions can include accepting or rejecting routes and setting attributes such as MED or communities. Export policies are important for controlling routing information sent to external networks and preventing unintended advertisements. Import policies serve the complementary purpose of controlling routes received from a neighbor. Together, these policies provide granular control over BGP route exchange.

Question 57. Which protocol provides Layer 2 neighbor discovery information between directly connected network devices?

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

Correct Answer: 3. LLDP

Explanation:
Link Layer Discovery Protocol (LLDP) allows directly connected network devices to advertise information about themselves over Layer 2. The information can include device identity, port identity, system capabilities, and management-related details. LLDP is useful for network discovery and troubleshooting because administrators can determine which neighboring device is connected to a particular interface. LLDP is independent of IP routing protocols such as OSPF and BGP. It is also different from proprietary neighbor-discovery mechanisms that may exist on particular vendor platforms. In Junos environments, LLDP can help verify physical network topology.

Question 58. What is the primary purpose of a policer in Junos OS?

1. To create OSPF adjacencies
2. To limit traffic according to configured rate or bandwidth parameters
3. To distribute MPLS labels
4. To calculate BGP routes

Correct Answer: 2. To limit traffic according to configured rate or bandwidth parameters

Explanation:
A policer is used to control traffic according to configured bandwidth or rate limits. In Junos, policers can be associated with firewall filters or other supported processing mechanisms to limit the amount of traffic that can pass at a specified rate. Traffic exceeding the configured limits can be discarded or handled according to the configured action. Policers are useful for controlling resource consumption, protecting infrastructure, and enforcing traffic-rate policies. They differ from routing policies, which operate on routing information, and from schedulers, which manage how traffic is transmitted through forwarding queues.

Question 59. Which IPv6 protocol replaces ARP for discovering the link-layer address associated with an IPv6 neighbor?

1. DHCPv6
2. ICMPv6 Neighbor Discovery
3. BGP
4. OSPFv3

Correct Answer: 2. ICMPv6 Neighbor Discovery

Explanation:
IPv6 does not use ARP. Instead, IPv6 hosts use Neighbor Discovery Protocol functionality carried through ICMPv6 to discover neighboring devices and resolve IPv6 addresses to link-layer addresses. Neighbor Discovery also supports functions such as router discovery, prefix discovery, and neighbor reachability detection. Neighbor Solicitation and Neighbor Advertisement messages are particularly important for address resolution and neighbor communication. DHCPv6 serves other address-configuration purposes, while OSPFv3 is an IPv6-capable routing protocol and BGP can exchange IPv6 routes through appropriate address families.

Question 60. Which Junos command is commonly used to identify the route selected for a specific destination prefix?

1. show chassis hardware
2. show interfaces diagnostics
3. show route <destination>
4. show configuration protocols

Correct Answer: 3. show route <destination>

Explanation:
The show route <destination> command can be used to inspect routing information for a specific destination prefix. It helps administrators determine whether a route exists, which protocol or source provided it, and which next hop and interface are associated with the selected route. Additional command options can provide more detailed information about route selection and protocol-specific attributes. This is a fundamental troubleshooting command because it allows administrators to verify how the control plane has resolved reachability toward a particular destination before investigating forwarding behavior or interface-level problems.