JN0-106 Practice Questions

In Junos, a prompt ending with the hash symbol (#) signifies that the user is in configuration mode, where set, edit, and commit commands are available.

A. Operational mode prompts end with >.

C. Shell mode prompts end with %.

D. Recovery mode uses a single-user shell prompt; not # within the CLI.

1. Juniper Networks, Junos OS CLI User Guide, 22.2R1, “CLI Modes and Prompts,” Table 4-1, p.21.

2. MIT OpenCourseWare, 6.829 Lecture Notes “Router CLIs,” slide 7 (describes Junos prompts).

The Routing Engine (RE) is the control-plane component of a Juniper device. It handles all management and protocol processing, maintains the routing and forwarding tables, and exchanges route information with the Packet Forwarding Engine (PFE); it does not forward transit or CoS-handled traffic itself.

B. CoS classification/queuing is performed in the PFE, not the RE.

C. Transit packet forwarding occurs in the PFE; the RE is not in the data path.

1. Juniper Networks, “Junos Platform Layered Architecture,” TechLibrary article, Table 1 (Routing Engine Functions).

2. Juniper Networks, “Junos OS Architecture Fundamentals,” Courseware AJER v21, Module 2, p. 2-6.

Each switch port in Junos operates as an independent half-duplex/ full-duplex Ethernet segment; therefore every port is its own collision domain. Unless VLAN tagging is configured, all ports on the same switch belong to one Layer-2 broadcast domain, so Ethernet broadcasts are flooded to every port.

A. Routers do not forward Layer-2 broadcasts, so they separate broadcast domains as well as collision domains.

B. VLANs segment broadcast domains; they do not reduce collision domains, which are already per switch port.

D. Broadcast domains exist at Layer-2; IPv6 simply uses multicast in place of broadcast, so the domain concept still applies.

1. Juniper TechLibrary, “Understanding Collision and Broadcast Domains,” Junos OS Enterprise Switching, Section: Ethernet LAN Fundamentals (2023-10-23), para. 1-3.

2. Juniper Day One: Switching Fundamentals, Ch. 2 “Layer-2 Forwarding,” p. 24-25.

The hierarchy set system archival configuration transfer-on-commit activates the automatic archive feature. Each time a commit succeeds, the current candidate configuration is copied to the locations defined under archive-sites, ensuring an immediate external backup.

A. commit synchronize pushes committed config to REs in a chassis cluster, not external servers.

B. transfer-interval schedules periodic (time-based) backups, not event-driven on each commit.

D. archive-sites specifies remote destinations but needs transfer-on-commit or transfer-interval to trigger the copy.

1. Junos OS System Management Configuration Guide, “Archiving and Restoring Configuration Files,” Section ‘transfer-on-commit’, https://www.juniper.net/documentation (accessed 14 May 2026).

2. JNCIS-ENT Courseware (JN0-349), Module 1, p. 1-29, “Automated Configuration Archiving.”

Secure Shell (SSH) provides encrypted transport, strong authentication, and protection against replay attacks, making it the supported protocol for secure, remote CLI sessions to Junos devices. Junos disables Telnet by default and recommends SSH for all administrative access.

A. FTP transfers files and is not used for interactive CLI access.

B. SNMP is for management polling/traps, not an interactive CLI.

C. Telnet offers CLI access but transmits data in clear text and is therefore insecure.

1. Junos OS System Basics Configuration Guide, “Using Secure Shell (SSH) to Access the Routing Engine,” Section Configuring SSH, https://www.juniper.net/documentation (accessed 14 May 2026).

2. Juniper Networks Day One: “Securing the Routing Engine,” Chapter 2, p. 17.

SNMPv3 adds User-based Security Model (USM) providing message authentication (MD5/SHA) and privacy (DES/AES encryption). Authentication protects against tampering; encryption prevents eavesdropping. User credentials (passwords/keys) are hashed or encrypted within the SNMPv3 message exchange, unlike the clear-text community strings of SNMPv1/v2c. Hence statements B and D are correct.

A. Plain-text community strings are used only in SNMPv1/v2c, not v3.

C. Additional security parameters (engine IDs, auth/priv keys) make SNMPv3 configuration more, not less, complex than v2c.

1. Junos OS SNMP MIBs and Agent Configuration Guide, “SNMPv3 Overview,” Section 2.1, p. 23–25 (Juniper Networks, 2023-04-20).

2. RFC 3414, “User-based Security Model for SNMPv3,” §1–3 (IETF, 2002).

3. Stanford EE284 Lecture Notes, “Network Management & SNMP,” slide 32–35 (auth/priv discussion).

ARP (Address Resolution Protocol) broadcasts a query for the MAC (Layer-2) address that corresponds to a known IPv4 address. The host owning that IP replies with its MAC, enabling the sender to populate its ARP cache and build the Layer-2 frame header for subsequent unicast traffic.

A. MPLS label assignment uses LDP or RSVP-TE, not ARP.

B. DNS resolves URLs to IP addresses, not ARP.

D. Reverse ARP (RARP) maps MAC-to-IP, but ARP performs IP-to-MAC.

1. Junos OS Layer 2 Switching Guide, “Understanding Address Resolution Protocol,” Section Overview, https://www.juniper.net/documentation (accessed 14 May 2026).

2. Comer, D.E., “Internetworking with TCP/IP Vol. 1,” 6th ed., Pearson, 2014, §5.2 (ARP Operation).

When you enter configuration mode, Junos copies the active configuration into a separate candidate configuration held in memory. All proposed edits are made to this candidate; they do not affect forwarding until a commit operation makes the candidate the new active configuration.

A. Backup configurations reside in the rollback archive, not in the candidate buffer.

B. The active configuration is the currently committed one, not the candidate.

C. The candidate becomes active immediately after commit, not after a reboot.

1. Juniper Networks, “Junos OS Fundamentals”, Chapter “Configuration Management”, pp. 38-40 (description of candidate configuration).

2. Juniper Networks, “Junos OS CLI User Guide”, Section “Committing a Configuration”, para. 1 (explains candidate vs. active).

The operational command clear log ospf-trace truncates the file—erasing all existing contents—then immediately reopens it so that OSPF trace messages keep being written; only the stored data is removed.

A. Command does not remove the file itself; it only empties it.

B. Runtime command never changes configuration traceoptions statements.

C. Logging continues after the file is cleared; it is not halted.

1. Juniper Networks, Junos OS CLI Reference 23.4R1, “clear log” command, Description ¶1-2.

2. Junos OS System Log Messages Guide 22.3, “Clearing System Log Files,” p.19.

The inet6.0 table in the exhibit contains only “Direct” and “Local” entries that correspond to the router’s own LAN segment; there are no learned (OSPF, BGP, RIPng, static, or default) prefixes. Because the routing table holds no destinations beyond the directly attached /64, the router cannot select a next hop for traffic that is outside that segment, so forwarding to any remote IPv6 network will fail.

C – No route for 2001:db8:22:108::/64 appears in the table; therefore no traffic can be forwarded to that prefix on ge-0/0/5.0.

D – The only connected entry shown is 2001:db8:22:107::/128 (the interface address), not the entire 2001:db8:22:107::/64 network; the /64 itself is not listed as connected.

1. Juniper Networks, Junos OS Routing Protocols Library, “show route” command description – Release 21.4R3, Section: Displaying IPv6 Routes, pp. 150-151.

2. Juniper Networks Day One: IPv6 for the Junos OS, Chapter 3 “Verifying the IPv6 Routing Table”, Example output discussion, pp. 41-42.

3. Juniper Education Services, Courseware “Junos Routing Essentials” (EDU-JRE), Module 2, Slide set “IPv6 Routing – Direct versus Learned Routes”.