Juniper JN0-106 Practice Test

JN0-106 practice test: what's covered

• Networking Fundamentals
• Junos OS Architecture
• CLI / J-Web
• Configuration
• Monitoring
• Routing
• Policy & Firewall Filters

Free JN0-106 sample questions

1. A network engineer connects ten hosts to a single Layer 2 switch and assigns them all to the same VLAN. How do the collision domains and the broadcast domain compare in this setup?

   • A. Each switch port is its own collision domain, while all ten hosts share one broadcast domain
   • B. All ten hosts share one collision domain and one broadcast domain
   • C. Each port is its own broadcast domain, while all hosts share one collision domain
   • D. The switch creates ten separate broadcast domains, one per port
   Show answer

   Correct: A. A switch segments collision domains per port (full-duplex, no contention), but by default a single VLAN is one broadcast domain, so broadcasts reach all members. A hub, not a switch, would put everyone in one collision domain.

2. A host needs to send a frame to another host on the same subnet but only knows the destination's IPv4 address. Which protocol resolves that IP address into the destination MAC address?

   • A. ARP (Address Resolution Protocol)
   • B. DNS (Domain Name System)
   • C. ICMP (Internet Control Message Protocol)
   • D. DHCP (Dynamic Host Configuration Protocol)
   Show answer

   Correct: A. ARP maps a known IPv4 address to the corresponding Layer 2 MAC address on the local segment. DNS resolves names to IPs, ICMP carries diagnostics/errors, and DHCP assigns addresses — none of them resolve IP-to-MAC.

3. An administrator must summarize the four contiguous networks 192.168.4.0/24, 192.168.5.0/24, 192.168.6.0/24 and 192.168.7.0/24 into a single route. Which summary (supernet) prefix covers exactly these four and no more?

   • A. 192.168.4.0/22
   • B. 192.168.4.0/23
   • C. 192.168.4.0/21
   • D. 192.168.0.0/22
   Show answer

   Correct: A. A /22 provides four contiguous /24 blocks (4,5,6,7) aligned on a multiple of four. A /23 covers only two /24s, a /21 covers eight (too broad), and 192.168.0.0/22 starts at the wrong boundary (covers 0-3).

4. A routing table on a Junos device contains both 10.0.0.0/8 and 10.1.1.0/24, and a packet arrives destined for 10.1.1.5. According to the longest-match rule, which route is used to forward the packet?

   • A. 10.1.1.0/24 because it is the most specific (longest) matching prefix
   • B. 10.0.0.0/8 because it was likely learned first
   • C. Both routes are used in a round-robin fashion
   • D. Neither route, because two overlapping prefixes cause the packet to be dropped
   Show answer

   Correct: A. Longest-match (most-specific) routing always selects the matching route with the longest prefix length, so /24 wins over /8 for 10.1.1.5. Route age, round-robin, and overlap-drop are not how destination lookup works.

5. A designer must choose a transport protocol for a real-time voice application that prioritizes low latency and can tolerate occasional packet loss without retransmission delays. Which protocol's characteristics fit best?

   • A. UDP, because it is connectionless and has no retransmission overhead
   • B. TCP, because its three-way handshake guarantees delivery
   • C. TCP, because flow control reduces latency
   • D. ARP, because it operates at Layer 2
   Show answer

   Correct: A. UDP is connectionless with no handshake, acknowledgements, or retransmissions, so it minimizes latency — ideal for real-time voice/video. TCP's reliability mechanisms add delay, and ARP is not a transport protocol at all.

Last updated: 2026-10-19

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