20+ practice questions focused on Tunnels — one of the most tested topics on the Juniper Networks Enterprise Routing and Switching, Specialist (JNCIS-ENT, JN0-352) (JNCIS-ENT) exam. Each question includes a detailed explanation so you learn why the right answer is correct.
Start Tunnels PracticeWhich interface naming convention is used for an IP-IP tunnel interface in Junos?
Explanation: In Junos, IP-IP tunnel interfaces are named with the prefix 'ip-' followed by the slot, PIC, and port numbers, such as ip-0/0/0. This naming convention distinguishes them from other tunnel types like GRE (gr-), IPsec (st-), and logical tunnel (lt-).
You are troubleshooting an IP-IP tunnel between two Junos devices where packets larger than 1476 bytes are being dropped without generating ICMP fragmentation needed messages. Which configuration command will resolve this issue by ensuring proper MTU adjustment?
Explanation: The issue is that IP-IP encapsulation adds 20 bytes of overhead (outer IP header), reducing the effective MTU on the tunnel to 1480 bytes (1500 - 20). Packets larger than 1476 bytes are dropped because the tunnel interface MTU is not adjusted, and ICMP fragmentation-needed messages are not generated. The solution is to either enable path-MTU discovery or reduce the tunnel interface MTU to account for the encapsulation overhead.
You want to run OSPF inside a GRE tunnel on Junos. After configuring the gr- interface, OSPF neighbor adjacencies fail to form. What is a common cause specific to tunnel interfaces in Junos?
Explanation: On Junos, GRE tunnel interfaces (gr-) default to OSPF network type NBMA or non-broadcast, which prevents OSPF from forming adjacencies without explicit neighbor configuration. Setting the tunnel interface's OSPF network type to point-to-point allows hellos to be sent as multicast and adjacencies to form. This is a common cause of OSPF over GRE failures specific to Junos.
An IP-IP tunnel is established between Router A and Router B. Traceroute packets traversing the tunnel show that all hops inside the tunnel are hidden. How does IP-IP encapsulation handle TTL by default on Junos?
Explanation: By default on Junos, IP-IP tunnels have TTL propagation disabled, meaning the TTL of the inner packet is not copied to the outer header. Instead, the outer header uses a fixed TTL (typically 64) and the inner TTL is not decremented by intermediate routers. This hides the inner hops from traceroute, as the traceroute only sees the tunnel endpoints.
You need to monitor the operational status and packet counters of a specific GRE tunnel interface named gr-0/0/0. Which operational mode command should you use?
Explanation: The command 'show interfaces gr-0/0/0 extensive' displays detailed operational status, packet counters, error statistics, and other extensive information for the specified interface. It is the standard Junos operational command to monitor a specific interface's health and traffic.
+15 more Tunnels questions available
Practice all Tunnels questions1. Baseline your knowledge
Start with 10 questions to gauge your current understanding of Tunnels. This tells you whether you need a concept refresher or just practice.
2. Review every explanation
For each question — right or wrong — read the full explanation. Understanding why an answer is correct is more valuable than knowing the answer itself.
3. Focus on exam traps
Tunnels questions on the JNCIS-ENT frequently use trap wording. Look for subtle differences in answers that test your precision, not just general knowledge.
4. Reach 80% consistently
Do repeated sessions until you score 80%+ three times in a row. Then move to mixed-mode practice to test cross-topic recall under realistic conditions.
The exact number varies per candidate. Tunnels is tested as part of the Juniper Networks Enterprise Routing and Switching, Specialist (JNCIS-ENT, JN0-352) (JNCIS-ENT) blueprint. Practicing with targeted Tunnels questions ensures you can handle any format or difficulty that appears.
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Difficulty is subjective, but Tunnels is a high-priority exam concept tested in multiple ways — direct recall, scenario analysis, and command-output interpretation. Consistent practice is the best way to build confidence.
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