JNCIS-ENT · domain
Tunnels
Practise Juniper Networks Enterprise Routing and Switching, Specialist (JNCIS-ENT, JN0-352) (JNCIS-ENT) Tunnels practice questions — original exam-style scenarios with answer choices, explanations, and analysis of common mistakes.
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What to know about Tunnels
Tunnels questions test whether you can apply the concept in context, not just recognise a definition.
How the topic appears in realistic exam-style scenarios.
Which detail in the question changes the correct answer.
How to eliminate plausible but wrong options.
How to connect the question back to the wider exam objective.
Watch out for
Common Tunnels exam traps
- ▸Answering from memory before reading the full scenario.
- ▸Missing a constraint such as cost, availability, security, scope or command context.
- ▸Choosing a broad answer when the question asks for the most specific fix.
- ▸Ignoring why the wrong options are tempting.
Question index
All Tunnels questions (51)
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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?
Medium2Which TWO factors must be carefully managed when running OSPF over a GRE tunnel interface on Junos devices? (Choose two.)
Hard3An administrator configures a GRE tunnel with a tunnel key enabled for security segmentation between two sites. The tunnel comes up, but traffic fails to pass. Debugging reveals that packets are dropped because the receiving router rejects the packets. What is the most probable configuration mismatch?
Hard4You are configuring a GRE tunnel over an IPv4 network, but you want to secure the GRE traffic using IPsec (GRE over IPsec). In Junos, how is this typically structured on SRX or MX devices?
Hard5You 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?
Medium6On an MX Series router, you configure a GRE tunnel that terminates on a routing instance (VRF). Where must the tunnel source and destination addresses be routable?
Hard7Which TWO parameters are mandatory when configuring a basic GRE tunnel interface in Junos? (Choose two)
Easy8When configuring OSPF over a GRE tunnel on Junos, which TWO configurations ensure stable neighbor adjacencies and correct route propagation? (Choose two)
Hard9You 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?
Hard10When configuring an IP-IP tunnel on Junos, can you run multicast routing protocols like PIM over the IP-IP tunnel?
Hard11You are configuring a GRE tunnel carrying IPv6 traffic over an IPv4 transport network (GRE over IPv4). Which interface family must be configured under the gr- interface unit?
Hard12Which THREE characteristics distinguish GRE tunnels from IP-IP tunnels on Junos devices? (Choose three)
Medium13You need to configure an IP-IP tunnel on a Junos device. Which interface prefix is designated for IP-IP tunnels in the Junos CLI?
Medium14You have configured an IP-IP tunnel, but traffic fails to pass through. You run 'show interfaces ip-0/0/0' and see that the output displays 'Input drops' incrementing rapidly. What is the most likely reason?
Medium15You are configuring an IP-IP tunnel on a Junos routing platform. Which statement correctly identifies how IP-IP encapsulation differs from GRE encapsulation?
Medium16An administrator has configured a GRE tunnel between two SRX Series devices. Traffic originating from behind the local security zone destined for the tunnel interface is being dropped by default security policies. Which action must be taken to ensure transit traffic can enter the GRE tunnel?
Hard17Which protocol number is used in the outer IP header for an IP-IP tunnel?
Easy18You are configuring a GRE tunnel and want to ensure that integrity checks are performed on the transmitted packets to detect corruption. Which parameter should you add to the tunnel configuration?
Medium19Which THREE factors should be considered when planning MTU size for traffic traversing a GRE tunnel? (Choose three)
Medium20An administrator notices that CPU utilization on the Routing Engine spikes when a high volume of transit traffic is directed through a locally terminated GRE tunnel on an MX router without inline services configured. What is the cause?
Hard21Which Junos operational mode command is used to verify the operational status and packet statistics of configured GRE tunnel interfaces?
Easy22An administrator needs to configure a basic GRE tunnel between two Junos devices across a routed IP network. Which interface family must be enabled on the physical transit interface to allow the GRE encapsulated packets to traverse the network?
Easy23Which TWO statements are true regarding Junos tunnel interface naming conventions? (Choose two)
Easy24Which command displays the configuration of a specific GRE tunnel interface in candidate configuration mode on Junos?
Easy25When troubleshooting a non-functional GRE tunnel on a Junos device, which TWO operational commands or verification steps are most effective for diagnosing the root cause? (Choose two)
Hard26You are troubleshooting a GRE tunnel on a Junos device and notice that traffic passing through the tunnel is being dropped due to packet size exceeding the path MTU. Which command can you use directly on the tunnel interface to prevent fragmentation issues by adjusting the MSS?
Medium27You are troubleshooting a GRE tunnel where traceroute shows packets looping between the tunnel endpoints. Which mechanism prevents routing loops in GRE tunnels on Junos?
Medium28Which TWO tools or commands can be used on Junos to verify the operational packet flow through a tunnel interface? (Choose two)
Easy29Which TWO actions must be performed when configuring a functional GRE tunnel between two Junos devices over an intermediate IP network? (Choose two.)
Hard30You have configured a GRE tunnel, and you want to verify that the tunnel source and destination parameters match what is expected. Which command shows the configured tunnel source and destination addresses?
Medium31Which THREE statements regarding IP-IP tunnels on Junos devices are accurate? (Choose three)
Medium32When configuring an IP-IP tunnel on a Junos device, what happens to the source and destination IP addresses of the original packet when it is encapsulated?
Hard33Which interface naming convention is used by Junos OS to identify a generic routing encapsulation (GRE) tunnel interface?
Easy34An 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?
Hard35You are designing a network where MTU issues across a GRE tunnel must be mitigated automatically without relying on manual interface MTU adjustments. Which feature can be enabled on Junos routers to dynamically adjust TCP Maximum Segment Size?
Hard36Which THREE parameters can be optionally configured on a Junos GRE tunnel interface (gr-) to enhance functionality or security? (Choose three.)
Medium37Which interface naming convention is used for an IP-IP tunnel interface in Junos?
Easy38Which Junos command displays the status of all configured tunnel interfaces on the device?
Easy39Which THREE statements are true regarding IP-IP encapsulation in Junos OS? (Choose three.)
Medium40What is the primary function of a Junos tunnel interface when used in conjunction with routing protocols?
Easy41Which THREE parameters are part of a standard Junos GRE tunnel interface configuration block? (Choose three)
Medium42Which TWO Junos configuration hierarchies are involved when setting up a functional GRE tunnel with an IP address? (Choose two)
Easy43When troubleshooting a non-functional IP-IP or GRE tunnel on a Junos routing device, which TWO diagnostic steps or commands are commonly utilized? (Choose two.)
Hard44You need to establish a point-to-point GRE tunnel between two Juniper MX Series routers. Which tunnel services type must be defined under the chassis configuration when using aggregated interface inline services?
Easy45Which Junos configuration statement defines the destination address of a GRE tunnel?
Easy46You configure a GRE tunnel between two routers. Router A can ping Router B's tunnel IP address successfully, but devices behind Router A cannot ping devices behind Router B across the tunnel. What is the most likely cause?
Medium47An enterprise network uses a GRE tunnel to connect two sites running OSPF. OSPF neighbor adjacencies fail to form over the GRE tunnel even though unicast pings between the tunnel endpoints succeed. Upon inspecting interface configurations, you notice that OSPF hellos are not being received by the peer. What is the most likely cause of this issue?
Hard48You need to configure a GRE tunnel that requires routing multiple distinct customer VRFs over a single GRE transport link. Which feature should you combine with the GRE tunnel interface?
Medium49What is the official protocol number assigned in the outer IP header for GRE encapsulation?
Easy50An administrator wants to verify that packets are successfully traversing a GRE tunnel interface. Which operational command displays packet counters specifically incrementing for the GRE encapsulation and decapsulation processes?
Medium51When configuring a GRE tunnel source and destination address on a Junos device, which configuration hierarchy is used?
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Frequently asked questions
- What does the Tunnels domain cover on the JNCIS-ENT exam?
- Tunnels questions test whether you can apply the concept in context, not just recognise a definition.
- How many questions are in this domain?
- This page lists all 51 Tunnels questions in the JNCIS-ENT question bank. The actual exam draws from this domain proportionally to its weighting in the official exam blueprint.
- What is the best way to practise this domain?
- Start with a short focused session (10 questions) to identify gaps, then work through explanations. Repeat with a longer session once the weak areas feel solid.
- Can I practise only Tunnels questions?
- Yes — the session launcher on this page filters questions to this domain only. Choose any session length for inline explanations and scoring.