View Full Juniper JN0-664 Exam Dumps and Practice Test Dumps.

 

Question 221

Which IS-IS level carries information between different areas?

1. Level 1
2. Level 2
3. Level 0
4. Level 3

Correct Answer: 2

Explanation:

IS-IS uses hierarchical levels to organize routing information. Level 1 routers primarily maintain routing information within their local area, while Level 2 routers provide connectivity between different IS-IS areas. A Level 2 router can therefore participate in inter-area routing and maintain information needed to reach destinations outside its local area. This hierarchy helps large networks scale by limiting detailed topology information to appropriate portions of the network. Understanding the distinction between Level 1 and Level 2 is important when designing or troubleshooting IS-IS domains, particularly when examining why a router can reach local destinations but requires Level 2 information for remote areas.

Question 222

Which BGP attribute identifies the router that originally generated reflected routes?

1. Cluster ID
2. Originator ID
3. Aggregator
4. Atomic Aggregate

Correct Answer: 2

Explanation:

The BGP Originator ID identifies the BGP router that originally originated a route in a route-reflection environment. When a route reflector reflects a route learned from a client, the Originator ID can preserve information about the original source router. This helps receiving routers recognize routes that originated locally and contributes to loop-prevention behavior. The Cluster ID serves a different purpose by identifying the route-reflector cluster and supporting loop prevention between route reflectors. Aggregator and Atomic Aggregate are associated with route aggregation information rather than identifying the original route-reflection source. These attributes should therefore not be treated as interchangeable.

Question 223

Which Junos command checks whether configuration syntax can commit successfully?

1. commit synchronize
2. commit check
3. commit confirmed
4. commit at

Correct Answer: 2

Explanation:

The Junos commit check command validates the candidate configuration without activating it. It is useful for detecting configuration errors before performing the actual commit operation. This provides an additional safety step when administrators are preparing complex changes. commit confirmed has a different purpose because it temporarily activates changes while requiring confirmation within a specified period. commit synchronize is associated with synchronizing configuration across supported routing-engine environments, while commit at schedules a commit for a specified time. Therefore, commit check is the appropriate command when the goal is simply to validate whether the candidate configuration can be committed.

Question 224

Which IPv6 message asks a neighboring host for link-layer information?

1. Router Advertisement
2. Neighbor Solicitation
3. Router Solicitation
4. Redirect

Correct Answer: 2

Explanation:

An IPv6 Neighbor Solicitation message is used by a host to obtain information about a neighboring IPv6 device, including its link-layer address. This functionality is part of ICMPv6 Neighbor Discovery and replaces the ARP-style address-resolution process used by IPv4. The destination neighbor can respond with a Neighbor Advertisement containing the relevant information. Router Advertisement messages communicate router and prefix information, while Router Solicitation messages are used by hosts to request Router Advertisements. Redirect messages provide more appropriate next-hop information under certain conditions. Recognizing these message roles is essential when troubleshooting IPv6 neighbor discovery.

Question 225

Which Junos command displays interface descriptions and operational states together?

1. show interfaces descriptions
2. show interfaces diagnostics optics
3. show interfaces extensive
4. show interfaces media

Correct Answer: 1

Explanation:

The show interfaces descriptions command provides a concise view of interface names, administrative or operational states, and configured descriptions. This makes it particularly useful when administrators need a quick overview of physical and logical interfaces without examining extensive interface statistics. Interface descriptions can document connected devices, circuit purposes, or other operational information. The command is different from show interfaces extensive, which provides much more detailed counters and interface information. Optical diagnostics focus on transceiver characteristics, while media information concerns supported interface media properties. The descriptions command is therefore well suited for quick interface inventory and status verification.

Question 226

Which BGP attribute can identify the router performing route aggregation?

1. Originator ID
2. Aggregator
3. Cluster List
4. Local Preference

Correct Answer: 2

Explanation:

The BGP Aggregator attribute can identify the router and autonomous system that performed route aggregation. When routes are summarized, this attribute can provide information about the device responsible for creating the aggregate route. It is associated specifically with aggregation behavior rather than general route preference. Originator ID and Cluster List are related to route reflection, while Local Preference influences route selection within an autonomous system. Understanding the Aggregator attribute can help administrators determine how a summarized route was created and trace aggregation-related information when analyzing BGP advertisements.

Question 227

Which Ethernet mechanism provides traffic visibility by copying selected frames?

1. Port mirroring
2. Link aggregation
3. BPDU protection
4. MAC limiting

Correct Answer: 1

Explanation:

Port mirroring copies selected network traffic from one or more source interfaces to a designated monitoring interface. A connected analysis device can then inspect the mirrored packets without becoming part of the normal forwarding path. This technique is commonly used for troubleshooting, traffic analysis, security monitoring, and protocol inspection. Link aggregation combines multiple physical interfaces for connectivity and capacity. BPDU protection focuses on unexpected spanning-tree messages, while MAC limiting controls learned Ethernet addresses. Port mirroring therefore provides visibility into traffic rather than changing the network’s normal forwarding topology or controlling endpoint access.

Question 228

Which routing protocol uses TLVs extensively for carrying structured information?

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

Correct Answer: 2

Explanation:

IS-IS uses Type-Length-Value, or TLV, structures extensively to carry routing information within its protocol messages. TLVs allow IS-IS to represent different types of information in a flexible and extensible format. This design has helped IS-IS support additional capabilities and address families without requiring a completely new message structure for every feature. Different TLVs can describe information such as reachability, metrics, authentication-related information, and other capabilities. BGP uses attributes and path information, while RIP uses its own message format and DHCP serves host configuration purposes. Understanding IS-IS TLVs is particularly valuable when analyzing protocol packets or advanced routing capabilities.

Question 229

Which Junos command displays the current system commit history?

1. show system commit
2. show system uptime
3. show system processes
4. show system users

Correct Answer: 1

Explanation:

The show system commit command displays information about configuration commits performed on a Junos device. Commit history can help administrators identify when configuration changes occurred and determine which users or processes were associated with those changes, depending on the available output. This is useful during troubleshooting and change auditing because network behavior can sometimes be correlated with a recent configuration modification. The command differs from system-uptime, process, and user commands, which provide other operational information. Reviewing commit history is therefore an important part of understanding configuration changes made over time.

Question 230

Which BGP capability allows graceful handling during control-plane restart?

1. Route Target
2. Graceful Restart
3. Add-Path
4. Community

Correct Answer: 2

Explanation:

BGP Graceful Restart allows routing platforms to preserve forwarding behavior temporarily while a BGP control-plane component restarts. The capability helps reduce unnecessary traffic disruption during certain restart conditions by allowing forwarding information to remain available while routing sessions recover. Neighboring BGP speakers exchange capability information to indicate support for graceful restart. Add-Path addresses advertisement of multiple paths, while Route Targets and Communities serve policy and VPN-related purposes. Graceful Restart therefore focuses specifically on maintaining forwarding continuity during supported control-plane restart events rather than changing normal BGP route selection.

Question 231

Which Junos command displays current routing protocol process information?

1. show system processes extensive
2. show interfaces terse
3. show route protocol
4. show chassis hardware

Correct Answer: 1

Explanation:

The show system processes extensive command provides detailed information about processes running on the Junos device. It can be useful when investigating CPU utilization, process activity, and operational behavior of system daemons. Routing protocols are handled by specific Junos processes, so process-level information can help identify abnormal resource consumption or unexpected daemon behavior. The command is broader than routing-table commands because it examines system processes rather than routes. Interface and chassis commands provide different operational information. Administrators should interpret process output carefully because high utilization can have many causes and requires correlation with other operational data.

Question 232

Which IPv4 service automatically provides hosts with network configuration?

1. DHCP
2. NTP
3. SNMP
4. Syslog

Correct Answer: 1

Explanation:

Dynamic Host Configuration Protocol, or DHCP, automatically provides IPv4 hosts with network configuration information. Depending on the deployment, DHCP can provide an IPv4 address, subnet information, default gateway, DNS server information, lease duration, and other options. This reduces the need for administrators to manually configure every endpoint. NTP provides time synchronization, SNMP supports network monitoring and management, and Syslog transports or records event messages. DHCP is therefore specifically associated with automated host configuration. Understanding DHCP is useful when troubleshooting why an endpoint has not received an address or other required network parameters.

Question 233

Which Junos mechanism can automatically revert after an unconfirmed change?

1. Rescue configuration
2. Commit confirmed
3. Configuration group
4. Candidate database

Correct Answer: 2

Explanation:

commit confirmed provides automatic rollback protection when a configuration change might affect remote management access or device operation. After the temporary commit, Junos starts a confirmation timer. If the administrator successfully verifies the change, another commit confirms it and prevents the automatic rollback. If confirmation does not occur before the timer expires, Junos returns to the previous committed state. This is especially valuable when making changes remotely because a connectivity problem can otherwise leave the administrator unable to correct the configuration. Rescue configurations and rollback files also support recovery, but they do not provide the same timed confirmation mechanism.

Question 234

Which multicast protocol establishes router-to-router multicast forwarding trees?

1. IGMP
2. PIM
3. MLD
4. DHCP

Correct Answer: 2

Explanation:

Protocol Independent Multicast, or PIM, establishes multicast forwarding relationships between routers. It uses information from the unicast routing system to determine reachable paths while building multicast distribution structures. Different PIM modes support different multicast deployment models. IGMP manages IPv4 multicast group membership between hosts and local routers, while MLD performs the corresponding membership function for IPv6. DHCP provides host configuration and has no role in constructing multicast distribution trees. PIM is therefore the protocol responsible for coordinating multicast forwarding between routers after hosts have indicated interest in receiving multicast traffic.

Question 235

Which BGP attribute contains the sequence of traversed autonomous systems?

1. MED
2. AS Path
3. Origin
4. Community

Correct Answer: 2

Explanation:

The BGP AS Path attribute records autonomous systems associated with the route’s advertisement history. As a route is propagated between autonomous systems, AS numbers can be added to the path. This information serves several purposes, including loop prevention and path-selection decisions. A receiving BGP router can reject a route if its own autonomous system number already appears in the path, helping prevent routing loops. MED influences path preference under specific conditions, Origin describes how the route entered BGP, and Community provides policy-related classification. AS Path is therefore the attribute specifically representing the autonomous-system sequence.

Question 236

Which Junos feature groups repeated configuration statements efficiently?

1. Configuration groups
2. Routing instances
3. Interface families
4. Firewall terms

Correct Answer: 1

Explanation:

Junos configuration groups allow administrators to define reusable configuration statements and apply them to multiple parts of the configuration. This can reduce duplication and simplify management when several interfaces, protocols, or devices require similar settings. Instead of entering the same statements repeatedly, an administrator can place common configuration into a group and reference it where needed. Routing instances create separate routing environments, interface families define protocol families supported on interfaces, and firewall terms specify packet-filtering conditions and actions. Configuration groups therefore focus on configuration reuse and consistency rather than routing separation or traffic filtering.

Question 237

Which IPv6 mechanism detects duplicate addresses before assignment?

1. Duplicate Address Detection
2. Prefix Delegation
3. Router Discovery
4. Multicast Registration

Correct Answer: 1

Explanation:

Duplicate Address Detection, or DAD, helps an IPv6 node determine whether another device is already using a proposed IPv6 address on the local link. The mechanism uses Neighbor Discovery messages before the address is considered usable. Detecting duplicates is important because two devices using the same IPv6 address can cause communication problems and unpredictable neighbor resolution. Prefix Delegation distributes prefixes, while Router Discovery helps hosts learn information from routers. Multicast registration concerns multicast membership rather than address uniqueness. DAD is therefore the IPv6 mechanism specifically intended to identify duplicate address usage.

Question 238

Which Junos feature separates routing tables for independent networks?

1. Routing instance
2. Configuration group
3. Interface family
4. Chassis cluster

Correct Answer: 1

Explanation:

A Junos routing instance provides a separate routing environment within a device. It can maintain its own routing information and support specific interfaces and routing protocols according to its configuration. This separation is useful in environments requiring independent routing domains, such as customer VPNs, management networks, or logically isolated services. A configuration group provides reusable configuration statements rather than routing separation. Interface families define supported protocol families, while chassis clustering addresses device-level redundancy. Routing instances therefore provide logical separation of routing information and forwarding behavior within a single Junos system.

Question 239

Which security technology authenticates users through EAP exchanges?

1. 802.1X
2. MACsec
3. IPsec
4. uRPF

Correct Answer: 1

Explanation:

IEEE 802.1X uses the Extensible Authentication Protocol framework to support authentication between an endpoint and an access device. In a typical deployment, the endpoint acts as the supplicant, the switch or access point acts as the authenticator, and an authentication server processes the credentials. EAP provides flexibility for different authentication methods while 802.1X controls access to the network connection. MACsec protects Ethernet frames, IPsec protects IP traffic, and uRPF validates source addresses against routing information. Therefore, 802.1X is the technology most directly associated with EAP-based network-access authentication.

Question 240

Which Junos component provides centralized control-plane management?

1. Packet Forwarding Engine
2. Routing Engine
3. Switching fabric
4. Physical interface module

Correct Answer: 2

Explanation:

The Routing Engine provides the centralized control-plane functions of a Junos device. It runs routing protocols, maintains routing information, handles system management functions, and communicates control information to the forwarding components. The Packet Forwarding Engine is responsible for high-speed packet processing, while the switching fabric and physical interface hardware provide other forwarding-plane functions. This separation between control and forwarding planes allows routing decisions and system management to operate independently from the high-speed forwarding path. Understanding the Routing Engine’s role is essential when studying Junos architecture and diagnosing whether a problem belongs to the control plane or forwarding plane.