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Question 81

Which Junos command can be used to display information about configured VLANs?

1. show vlans
2. show vlan configuration
3. show ethernet vlans
4. show switching vlan

Correct Answer: 1

Explanation

The show vlans command is used on supported Junos switching platforms to display information about configured VLANs. VLAN information can include VLAN names, identifiers, associated interfaces, and other relevant details depending on the platform and configuration. Administrators can use this command when troubleshooting Layer 2 segmentation or verifying whether a VLAN has been configured correctly. VLAN verification is especially important when investigating connectivity problems between hosts because incorrect VLAN membership or tagging can prevent devices from communicating as expected across a switched network.

Question 82

Which type of interface is normally connected to an end-user device belonging to a single VLAN?

1. Trunk interface
2. Access interface
3. Loopback interface
4. Tunnel interface

Correct Answer: 2

Explanation

An access interface is typically used to connect an end-user device such as a computer, printer, or server to a specific VLAN. Traffic arriving from the endpoint is associated with the configured VLAN, while the endpoint normally does not need to understand VLAN tagging. Access interfaces are commonly used at the edge of a switched network. Trunk interfaces serve a different purpose because they can transport traffic for multiple VLANs. Properly assigning access interfaces to the intended VLAN is important for maintaining network segmentation and connectivity.

Question 83

Which protocol prevents Layer 2 switching loops in Ethernet networks?

1. STP
2. BGP
3. OSPF
4. ARP

Correct Answer: 1

Explanation

Spanning Tree Protocol, or STP, helps prevent Layer 2 loops in Ethernet switching networks. Redundant physical links can create loops that cause broadcast storms, duplicate frames, and unstable MAC address learning. STP identifies redundant paths and places selected interfaces into a blocking state while maintaining them as potential backup paths. If an active path fails, STP can allow an alternate path to become active. Junos switching platforms support spanning-tree technologies to improve Layer 2 network stability and provide controlled redundancy.

Question 84

Which command can be used to display spanning-tree information on a Junos switching device?

1. show spanning-tree bridge
2. show spanning-tree interface
3. show spanning-tree
4. show stp status

Correct Answer: 3

Explanation

The show spanning-tree command is used to display spanning-tree information on supported Junos switching platforms. The output can provide details about spanning-tree operation, bridge information, interfaces, and states. Administrators can use this information to determine whether spanning tree is operating correctly and whether particular interfaces are forwarding or blocking. This is useful when troubleshooting Layer 2 loops or unexpected switching behavior. Additional command options can provide more specific information about interfaces or spanning-tree instances when a detailed investigation is required.

Question 85

Which address identifies a network interface at Layer 2?

1. IP address
2. MAC address
3. Port number
4. VLAN name

Correct Answer: 2

Explanation

A MAC address identifies a network interface at the data-link layer. Ethernet devices use MAC addresses to deliver frames within a local Layer 2 network. Switches learn MAC addresses and associate them with physical interfaces, allowing frames to be forwarded efficiently. IP addresses operate at Layer 3 and are used for communication between different IP networks. Understanding the distinction between MAC and IP addressing is essential for troubleshooting because Layer 2 switching and Layer 3 routing use different types of addressing information.

Question 86

Which protocol is used to discover the MAC address associated with an IPv4 address?

1. DNS
2. ARP
3. DHCP
4. NTP

Correct Answer: 2

Explanation

ARP, or Address Resolution Protocol, is used to discover the MAC address associated with an IPv4 address on a local network. When a device needs to communicate with another local IPv4 host, it can send an ARP request asking which device owns the target IP address. The appropriate device responds with its MAC address, allowing Ethernet communication to proceed. Junos devices maintain ARP information that can be examined during troubleshooting. ARP is specifically associated with IPv4 address resolution and is different from DNS, which handles name resolution.

Question 87

Which Junos command can display ARP entries?

1. show arp
2. show ip arp
3. show interfaces arp
4. show network arp-table

Correct Answer: 1

Explanation

The show arp command displays ARP information maintained by a Junos device. The output can show IPv4 addresses and their associated MAC addresses along with interface information. Administrators can use ARP information when troubleshooting local connectivity issues, duplicate addressing problems, or incomplete address resolution. If an expected ARP entry is missing, it may indicate a problem with local connectivity, addressing, or ARP communication. Checking ARP information alongside interface and routing information can provide a clearer picture of where a connectivity problem exists.

Question 88

Which type of address is used by IPv4 to identify a network interface logically?

1. MAC address
2. IP address
3. VLAN identifier
4. TCP port

Correct Answer: 2

Explanation

An IPv4 address provides logical Layer 3 identification for a network interface. It consists of a network portion and a host portion determined by the subnet mask or prefix length. Routers use IPv4 addresses to make forwarding decisions and deliver packets between different networks. Unlike MAC addresses, which are primarily used for local Ethernet communication, IP addresses support communication across interconnected networks. Correct IP addressing and subnetting are fundamental to network connectivity and are important concepts for administrators working with Junos devices.

Question 89

Which subnet mask corresponds to the IPv4 prefix length /24?

1. 255.255.0.0
2. 255.255.255.0
3. 255.0.0.0
4. 255.255.255.252

Correct Answer: 2

Explanation

An IPv4 /24 prefix corresponds to the subnet mask 255.255.255.0. The /24 notation indicates that the first 24 bits of the address represent the network portion, leaving 8 bits for host addressing. A /24 IPv4 network contains 256 total addresses, although the number of traditionally usable host addresses is smaller because network and broadcast addresses have specific purposes. Understanding prefix lengths and subnet masks is essential when configuring interfaces, designing networks, and interpreting routing-table entries on Junos devices.

Question 90

How many bits are contained in an IPv4 address?

1. 16
2. 32
3. 48
4. 64

Correct Answer: 2

Explanation

An IPv4 address contains 32 bits. These bits are commonly represented as four decimal octets separated by periods, such as 192.0.2.1. Each octet represents 8 bits, resulting in 32 bits in total. The address is divided into network and host portions based on the subnet mask or prefix length. IPv4 addressing is fundamental to Layer 3 networking because routers use these addresses to identify source and destination networks. Understanding the basic structure of IPv4 addresses helps administrators configure interfaces and interpret routing information.

Question 91

How many bits are contained in an IPv6 address?

1. 32
2. 64
3. 96
4. 128

Correct Answer: 4

Explanation

An IPv6 address contains 128 bits, providing a significantly larger address space than IPv4. IPv6 addresses are normally represented using hexadecimal notation divided into groups separated by colons. The larger address space supports a very large number of unique addresses and reduces the pressure associated with IPv4 address exhaustion. IPv6 also introduces features such as simplified header processing and extensive support for hierarchical addressing. Junos devices support IPv6 configuration and routing, making knowledge of IPv6 addressing important for modern network administration.

Question 92

Which IPv6 address type is used for communication with all nodes on a local link?

1. Multicast
2. Anycast
3. Unicast
4. Broadcast

Correct Answer: 1

Explanation

IPv6 uses multicast rather than broadcast for communicating with groups of devices, including all nodes on a local link. The well-known link-local all-nodes multicast address is ff02::1. Multicast allows packets to be delivered to a defined group of recipients without requiring a broadcast mechanism. IPv6 uses several multicast groups for functions such as neighbor discovery. Understanding IPv6 multicast is important because IPv6 does not use IPv4-style broadcast addresses. This difference affects how common network discovery and control functions operate.

Question 93

Which IPv6 address range is used for link-local addresses?

1. FE80::/10
2. FC00::/7
3. 2000::/3
4. FF00::/8

Correct Answer: 1

Explanation

The IPv6 FE80::/10 range is reserved for link-local addresses. Link-local addresses are used for communication between IPv6 devices on the same local link and are not normally routed between different links. They are automatically generated or configured on IPv6-enabled interfaces and are important for functions such as Neighbor Discovery and routing-protocol operation. Because link-local addresses are limited to a local link, a zone or interface may be required when referring to them in certain contexts. Understanding IPv6 address scopes is important for troubleshooting IPv6 connectivity.

Question 94

Which protocol is used by IPv6 for neighbor discovery and related functions?

1. ARP
2. NDP
3. DHCPv4
4. FTP

Correct Answer: 2

Explanation

Neighbor Discovery Protocol, or NDP, performs several functions in IPv6 networks that are associated with ARP and other mechanisms in IPv4. NDP uses ICMPv6 messages to discover neighboring devices, determine link-layer addresses, identify routers, and perform address-related functions. IPv6 does not use ARP for neighbor discovery. Understanding NDP is important when troubleshooting IPv6 communication because neighbor relationships and router discovery depend on these ICMPv6 mechanisms. Junos devices support IPv6 neighbor discovery as part of their IPv6 networking functionality.

Question 95

Which protocol is commonly used to automatically assign IPv6 configuration information to hosts?

1. DHCPv6
2. FTP
3. ARP
4. BGP

Correct Answer: 1

Explanation

DHCPv6 provides dynamic configuration services for IPv6 clients. Depending on the network design, DHCPv6 can provide addressing and other configuration information such as DNS-related parameters. IPv6 networks can also use Stateless Address Autoconfiguration, or SLAAC, allowing hosts to generate addresses using information advertised by routers. DHCPv6 and SLAAC therefore provide different mechanisms for IPv6 configuration. Understanding both is useful when troubleshooting why an IPv6 host has or does not have the expected addressing and network-service information.

Question 96

Which command can be used to display IPv6 neighbor information on a Junos device?

1. show ipv6 neighbors
2. show ipv6 neighbor
3. show ndp
4. show inet6 arp

Correct Answer: 3

Explanation

The show ndp command can be used on Junos devices to display IPv6 Neighbor Discovery information. It provides information about neighboring IPv6 devices and their associated link-layer addresses. This information can be useful when troubleshooting IPv6 connectivity and verifying whether a local device has successfully discovered its neighbors. Because IPv6 uses NDP instead of ARP, administrators need to use IPv6-specific operational commands when investigating neighbor relationships. Examining NDP information alongside interface and routing information can help identify local IPv6 communication problems.

Question 97

Which protocol provides reliable, connection-oriented transport for applications?

1. UDP
2. IP
3. TCP
4. ICMP

Correct Answer: 3

Explanation

Transmission Control Protocol, or TCP, provides reliable, connection-oriented transport between applications. It uses mechanisms such as sequence numbers, acknowledgments, retransmissions, and flow control to help ensure that data arrives correctly and in order. TCP is commonly used by applications that require reliable delivery, including many web, file-transfer, and remote-access services. UDP provides a connectionless transport service without the same reliability mechanisms. Understanding the difference between TCP and UDP helps administrators troubleshoot application connectivity and interpret traffic behavior across a network.

Question 98

Which transport protocol is connectionless and does not provide built-in reliable delivery?

1. TCP
2. UDP
3. HTTP
4. SSH

Correct Answer: 2

Explanation

User Datagram Protocol, or UDP, is a connectionless transport protocol that does not provide TCP-style acknowledgments, sequencing, or retransmission mechanisms. Because it has less protocol overhead, UDP can be useful for applications where low latency or simple message delivery is important. Applications using UDP may implement their own reliability mechanisms when needed. Common examples include DNS queries and certain real-time applications. Network administrators should understand that successful UDP transmission does not guarantee application-level delivery in the same way that TCP’s reliability mechanisms attempt to provide.

Question 99

Which protocol is commonly used to securely transfer files over an SSH connection?

1. SCP
2. TFTP
3. FTP
4. HTTP

Correct Answer: 1

Explanation

Secure Copy Protocol, or SCP, provides file transfer using the security mechanisms of SSH. It can be used to securely transfer configuration files, software packages, logs, and other files between systems that support the protocol. Because the transfer occurs through an encrypted SSH session, SCP provides stronger protection than traditional FTP or TFTP. Administrators may use secure file-transfer methods when moving files to or from network devices. The exact file-transfer capabilities available can vary by Junos release and platform.

Question 100

Which Junos command is commonly used to display the status of configured BGP sessions?

1. show bgp summary
2. show bgp status
3. show routing bgp sessions
4. show protocol bgp

Correct Answer: 1

Explanation

The show bgp summary command provides a concise view of BGP sessions configured on a Junos device. It can show information about configured peers, session states, autonomous systems, and route counts. Administrators can use this command as an initial troubleshooting step when verifying whether BGP neighbors have successfully established sessions. If a session is not established, more detailed commands can then be used to examine the specific peer and investigate possible configuration, connectivity, authentication, or policy issues. This makes the summary command useful for quickly assessing overall BGP status.