JNCIS-ENT Tunnels Practice Test 3 — 15 Questions

Question 1

Which TWO parameters are mandatory when configuring a basic GRE tunnel interface in Junos? (Choose two)

Accepted Answer

Tunnel destination IP address. Configuring a GRE tunnel requires defining both the tunnel source IP address and the tunnel destination IP address.

Answer

GRE keepalive interval timer

Answer

Routing protocol authentication key

Answer

IPsec security association profile

Question 2

An 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?

Accepted Answer

show interfaces gr-0/0/0. Interface statistics command 'show interfaces gr-0/0/0' shows input and output packet and byte counters.

Answer

Placeholder note for JSON formatting compliance

Answer

show security flow session interface gr-0/0/0

Answer

show chassis traffic-counters

Answer

show gre traffic

Question 3

Which THREE characteristics distinguish GRE tunnels from IP-IP tunnels on Junos devices? (Choose three)

Accepted Answer

GRE supports optional features like checksums and keys.. GRE supports multicast, has an optional checksum/key, and protocol type field, whereas IP-IP is simpler, supports protocol 4, and lacks multicast support.

Answer

IP-IP tunnels require a specialized Routing Engine hardware card.

Answer

IP-IP tunnels inherently encrypt all transmitted data payloads.

Question 4

When 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)

Accepted Answer

Verify that the routing table has an active path to the remote tunnel destination IP address.. Checking interface extensive statistics and verifying route reachability to the tunnel destination are primary troubleshooting steps.

Answer

Execute 'clear gre statistics' to restart the tunnel encapsulation engine.

Answer

Check that the RSVP bandwidth reservation is set to 100% on the tunnel interface.

Answer

Verify that the BGP AS path matches the tunnel ID.

Question 5

Which THREE factors should be considered when planning MTU size for traffic traversing a GRE tunnel? (Choose three)

Accepted Answer

Adjusting TCP MSS or tunnel interface MTU helps prevent packet fragmentation and drop issues.. GRE adds overhead, DF bit behavior matters, and fragmenting or adjusting MSS avoids drops.

Answer

GRE tunnels automatically expand physical interface MTU sizes to accommodate overhead.

Answer

IP-IP headers are larger than GRE headers, requiring larger MTU adjustments.

Question 6

Which THREE statements regarding IP-IP tunnels on Junos devices are accurate? (Choose three)

Accepted Answer

IP-IP encapsulation uses IP protocol number 4.. IP-IP uses protocol 4, encapsulates IP in IP, and does not support multicast.

Answer

IP-IP tunnels require a mandatory 4-byte key field in the header.

Answer

IP-IP tunnels provide built-in hardware encryption by default.

Question 7

Which TWO Junos configuration hierarchies are involved when setting up a functional GRE tunnel with an IP address? (Choose two)

Accepted Answer

edit chassis. Interfaces hierarchy configures both the gr- tunnel unit parameters and the physical/transport routing.

Answer

edit system services tftp

Answer

edit firewall

Answer

edit protocols bgp

Question 8

Which TWO tools or commands can be used on Junos to verify the operational packet flow through a tunnel interface? (Choose two)

Accepted Answer

show interfaces gr-0/0/0 extensive. show interfaces extensive and monitor traffic interface are standard troubleshooting tools.

Answer

show chassis alarms

Answer

request system snapshot

Answer

show route summary

Question 9

When configuring OSPF over a GRE tunnel on Junos, which TWO configurations ensure stable neighbor adjacencies and correct route propagation? (Choose two)

Accepted Answer

Ensure that the tunnel interface has a valid IP address matching the subnet of the remote tunnel end.. Setting the OSPF network type to point-to-point and ensuring correct subnet assignment/reachability are critical.

Answer

Disable IP-IP encapsulation on the OSPF routing options.

Answer

Enable BGP graceful restart on the tunnel interface.

Answer

Set the OSPF dead interval to 1 second globally.

Question 10

Which THREE parameters are part of a standard Junos GRE tunnel interface configuration block? (Choose three)

Accepted Answer

family inet address <ip-address>. Source IP, destination IP, and family inet address are part of the gr- unit configuration.

Answer

gre-key <number>

Answer

encapsulation-type ipsec

Question 11

An 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?

Accepted Answer

family inet. The physical transit interface must have the inet family enabled to route the outer IP packets containing the GRE encapsulation.

Answer

family mpls

Answer

family iso

Answer

family ccc

Question 12

Which interface naming convention is used by Junos OS to identify a generic routing encapsulation (GRE) tunnel interface?

Accepted Answer

gr-. Junos uses the gr- prefix for GRE tunnel interfaces.

Answer

lt-

Answer

st-

Answer

ip-

Question 13

You 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?

Accepted Answer

set interfaces gr-0/0/0 unit 0 family inet mtu 1400. The mtu and tcp-mss settings on the gr- interface or applying path-mtu-discovery helps manage packet sizes, but setting tcp-mss under the logical interface or routing options is typical. Alternatively, setting tunnel MTU properly is managed on the gr- interface.

Answer

set interfaces gr-0/0/0 unit 0 tunnel destination 192.168.1.2

Answer

set protocols gre path-discovery enable

Answer

set routing-options ip-options drop

Question 14

An 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?

Accepted Answer

Configure a security policy from the internal zone to the zone containing the gr- interface allowing all traffic.. Security zones and policies must permit traffic from the internal security zone to the zone where the gr- interface resides, or configure appropriate self-traffic/zone policies.

Answer

Disable flow-based mode globally on the SRX Series device.

Answer

Enable proxy-arp on the physical interface.

Answer

Add the gr- interface to the junos-default security zone.

Question 15

You need to configure an IP-IP tunnel on a Junos device. Which interface prefix is designated for IP-IP tunnels in the Junos CLI?

Accepted Answer

ip-. IP-IP tunnels use the ip- interface prefix.

Answer

mt-

Answer

gr-

Answer

st-