Juniper Networks JN0-106: Junos, Associate (JNCIA-Junos)

Last checked November 10, 2026 against the official Juniper Networks exam page.

1. Question 1Networking Fundamentals

   A small office replaces a hub with a 24-port Layer 2 switch. An engineer asks how the collision domains change. Which statement is correct?

   1. AEach switch port is its own collision domain, so hosts on different ports do not contend for the medium
   2. BAll 24 ports form one collision domain, because the switch floods unknown unicast frames to every port
   3. CThe switch keeps the hub's single collision domain but blocks broadcast frames on every port
   4. DThe switch creates one collision domain for each VLAN, while the former hub's single domain stays in place
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   Correct answer: A

   Each switch port is its own collision domain, so hosts on different ports do not contend for the medium. Flooding does not merge the ports into one domain, a switch forwards broadcasts rather than blocking them by default, and VLANs create broadcast domains rather than collision domains.

2. Question 2Junos OS Fundamentals

   An OSPF hello packet arrives on an interface of a Junos router. Which component ultimately processes this packet?

   1. AThe Routing Engine, because routing protocol packets are exception traffic passed up from the PFE
   2. BThe Packet Forwarding Engine, which performs the first lookup in the forwarding table for the packet
   3. CThe chassis daemon, which must validate the neighbor before any routing protocol packet is accepted
   4. DThe management daemon, which logs the hello in the system log before the packet is handled
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   Correct answer: A

   OSPF hellos are routing protocol packets, which the PFE passes up to the Routing Engine as exception traffic. The PFE may perform the first lookup, but the Routing Engine runs OSPF, and the chassis and management daemons do not process routing protocol hellos.

3. Question 3User Interfaces

   An operator wants to see only the lines containing ge-0/0/0 from the output of show interfaces terse. Which command accomplishes this?

   1. Ashow interfaces terse | count
   2. Bshow interfaces terse | except ge-0/0/0
   3. Cshow interfaces terse | match ge-0/0/0
   4. Dshow interfaces terse | find ge-0/0/0
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   Correct answer: C

   The match pipe displays only the lines that contain the given text. except removes the matching lines, count reports how many lines are in the output rather than showing them, and find starts the output at the first match and keeps everything below it.

4. Question 4Configuration Basics

   A junior administrator needs an operator account that can display device operational status but cannot change anything. Which login class configuration meets this requirement?

   1. Aset system login class ops permissions all
   2. Bset system login class ops permissions configure
   3. Cset system login class ops permissions view
   4. Dset system login class ops permissions maintenance
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   Correct answer: C

   The view permission allows show commands for operational state and does not allow changes. all grants every permission, configure allows editing the configuration, and maintenance allows maintenance actions such as reboots.

5. Question 5Operational Monitoring and Maintenance

   An administrator sees steadily rising input errors with CRC errors on interface ge-0/0/0 while traffic volume is light. Which action is the best first step?

   1. ACheck the cable, optic and link speed or duplex settings on both ends of the link
   2. BAdd a static route that avoids the interface so that traffic stops using the link entirely
   3. CChange the OSPF cost on the interface so that routing prefers another path immediately
   4. DRaise the interface MTU to 9192 bytes so that frames stop being dropped at the port
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   Correct answer: A

   CRC errors usually point to a physical or link-layer problem such as a damaged cable, a faulty optic, or a speed or duplex mismatch. Changing the MTU, adding a static route, or changing the OSPF cost does not fix the underlying error.