📘 Free JN0-351-JNCIS-ENT Sample Questions
Referring to the exhibit, which router will become the OSPF BDR if all routers are powered on at the same time?
A
R4
B
R1
C
R3
D
R2
Correct Answer:
C. R3
What is the management IP address of the device shown in the exhibit?
A
10.210.20.233
B
172.23.12.100
C
128.0.0.1
D
172.23.11.10
Correct Answer:
A. 10.210.20.233
Which three protocols support BFD? (Choose three.)
A
RSTP
B
BGP
C
OSPF
D
LACP
E
FTP
Correct Answer:
B. BGP
Explanation:
BCD is correct because BGP, OSPF, and LACP explicitly support BFD for rapid failure detection in their
operation.
BGP (Border Gateway Protocol) utilizes BFD (Bidirectional Forwarding Detection) to enhance the reliability of
path detection and route convergence. The integration allows for swift failure detection, contributing to the
protocol's robustness in WAN environments. Similarly, OSPF (Open Shortest Path First) implements BFD to
expedite the failure detection of OSPF neighbors, ensuring minimal downtime and route recalculation delays.
LACP (Link Aggregation Control Protocol) leverages BFD to rapidly identify link failures within channel
groups, optimizing throughput and enhancing link redundancy.
In contrast, RSTP (Rapid Spanning Tree Protocol) primarily focuses on preventing loops in a network and does
not directly incorporate BFD principles. It relies on its own mechanisms for topology changes, such as rapid
transition states, rather than utilizing BFD's high-frequency hello messages for link failure detection. FTP (File
Transfer Protocol) is an application layer protocol designed for file transfers and does not pertain to network
failure detection, thus making it inherently incompatible with the objectives of BFD.
References:
https://www.juniper.net/documentation/en_US/junos/topics/topic-map/bfd.html
https://www.cisco.com/c/en/us/td/docs/iosxr/ncs5500/bfd/bfd-overview.html
https://www.ietf.org/rfc/rfc5880.txt
Which statement is correct about graceful Routing Engine switchover (GRES)?
A
The PFE restarts and the kernel and interface information is lost.
B
GRES has a helper mode and are starting mode.
C
. When combined with NSR, routing is preserved and the new master RE does not restart rpd.
D
With no other high availability features enabled, routing is preserved and the new master RE does not restart rpd.
Correct Answer:
C. . When combined with NSR, routing is preserved and the new master RE does not restart rpd.
Explanation:
Option C is correct because graceful Routing Engine switchover (GRES), when paired with Non-Stop Routing
(NSR), ensures that routing processes remain uninterrupted and that the new master Routing Engine (RE)
operates without restarting the route protocol daemon (rpd).
and resilience in network operations.
Critique of Other Options:
Justification for Option C:GRES is designed to enhance the high availability of network services by allowing a
seamless transition between Routing Engines during failover conditions. When combined with NSR, which
maintains the state of routing protocols, GRES enables uninterrupted routing by preserving the active routing
table and avoiding the restart of rpd. This capability minimizes downtime, ensuring optimal service continuity
Option A: Incorrect. While the Packet Forwarding Engine (PFE) may restart during a failover, GRES is
specifically designed to maintain state information such as routing and interface data, preventing data loss
that would affect continuity.
Option B: Incorrect. GRES does not have defined modes such as "helper mode" or "starting mode." The
mechanism focuses on enhancing resilience without specifying these operational modes.
Option D: Incorrect. This option suggests that routing is preserved without any high availability features,
contradicting the fundamental characteristic of GRES, which necessitates NSR for effective routing
preservation during a switchover.
References:
https://www.juniper.net/documentation/en_US/junos/topics/concept/gres-overview.html
https://www.juniper.net/documentation/en_US/junos/topics/concept/nsr-overview.html
https://www.juniper.net/documentation/en_US/junos/topics/task/configuration/gress-nsr-config.html
Which statement is correct about controlling the routes installed by a RIB group?
A
An import policy is applied to the RIB group.
B
Only routes in the last table are installed
C
A firewall filter must be configured to install routes in the RIB groups.
D
An export policy is applied to the RIB group.
Correct Answer:
A. An import policy is applied to the RIB group.
Explanation:
A is correct because an import policy effectively governs which routes are allowed into the RIB group, thereby
shaping the routing information stored in the Routing Information Base.
The Route Information Base (RIB) is essential for managing and controlling route dissemination within a
network. Applying an import policy to a RIB group determines the routes that will be accepted into that group,
thus enabling granular control over routing decisions. This mechanism allows for the filtering and
manipulation of incoming routes based on specified criteria, such as prefix match, protocol type, or other
attributes, effectively tailoring the routing landscape according to network requirements.
Evaluation of Incorrect Options:
References:
B. Only routes in the last table are installed: This statement is misleading as RIB groups may consist of routes
from multiple sources, not exclusively the last updated table. The RIB is designed to consolidate routes from
various routing tables, meaning it does not restrict routing information strictly to the most recent entries.
C. A firewall filter must be configured to install routes in the RIB groups: This option incorrectly conflates
firewall policies with route management. While firewall filters are critical for security and traffic control, they
do not influence the installation of routes into RIB groups; instead, routing decisions are fundamentally
handled through routing protocols and policies.
D. An export policy is applied to the RIB group: This proposition is incorrect because export policies typically
dictate how routes are shared out from a RIB group rather than controlling the incoming routes. Export
policies are employed for propagating information across different routing domains, not for the installation
process within a RIB group.
https://www.juniper.net/documentation/en_US/junose/topics/concept/routing-information-base.html
https://www.juniper.net/documentation/en_US/junos/topics/task/configuration/rib-groups-creating.html
https://www.juniper.net/documentation/en_US/junos/topics/task/configuration/policy-importing.html
You are using OSPF to advertise the subnets that are used by the Denver and Dallas offices. The routers that are
directly connected to the Dallas and Denver subnets are not advertising the connected subnets.
Referring to the exhibit, which two statements are correct? (Choose two.)
A
. Create static routes on the switches using the local vMX router's loopback interface for the next hop.
B
Configure and apply a routing policy that redistributes the Dallas and Denver subnets using Type 5 LSAs.
C
Configure and apply a routing policy that redistributes the connected Dallas and Denver subnets.
D
Enable the passive option on the OSPF interfaces that are connected to the Dallas and Denver subnets.
Correct Answer:
C. Configure and apply a routing policy that redistributes the connected Dallas and Denver subnets.
You want to verify prefix information being sent from 10.36.1.4.
Which two statements are correct about the output shown in the exhibit? (Choose two.)
A
The routes displayed have traversed one or more autonomous systems.
B
The output shows routes that were received prior to the application of any BGP import policies.
C
. The output shows routes that are active and rejected by an import policy.
D
The routes displayed are being learned from an IBGP peer.
Correct Answer:
A. The routes displayed have traversed one or more autonomous systems.
What is the default keepalive time for BGP?
A
10 seconds
B
60 seconds
C
30 seconds
D
90 seconds
Correct Answer:
C. 30 seconds
Explanation:
The correct answer is C, 30 seconds, as it represents the default keepalive time for BGP (Border Gateway
Protocol).
BGP utilizes a keepalive mechanism to ensure that peers remain active within a routing session. The default
keepalive interval is set to 30 seconds, allowing for periodic assurances that the connection is still functional,
while also striking a balance between responsiveness and resource consumption. Determining this interval is
critical because excessively short intervals could lead to unnecessary processing overhead, while excessively
long intervals may delay the detection of failed peers.
Evaluation of Incorrect Options:
Option A: 10 seconds: This interval is too aggressive for BGP's operational needs, increasing the processing
load on routers unnecessarily. Such configurations are technically possible, but BGP defaults are optimized
for broader network stability and scalability, thus rendering this option incorrect.
deviates from BGP's established norms.
enterprise settings.
fault detection in BGP communications.
References:
bgp.html
Option B: 60 seconds: While this value could be used in certain configurations, it extends the detection time
for failures beyond the default, which is not ideal in environments requiring rapid convergence. This choice
Option D: 90 seconds: This interval significantly hinders reliable communication, increasing the risk of
prolonged network disruptions. It is incompatible with BGP's designed efficiency, making it less practical in
In conclusion, the choice of a 30-second keepalive interval is instrumental for optimal performance and rapid
https://www.cisco.com/c/en/us/support/docs/ip/border-gateway-protocol-bgp/13526-keepalive-timers-in-
https://www.juniper.net/documentation/en_US/junos/topics/topic-map/bgp.html
https://www.cloudflare.com/learning/bgp/how-bgp-works/
Which two statements are correct about tunnels? (Choose two.)
A
BFD cannot be used to monitor tunnels.
B
Tunnel endpoints must have a valid route to the remote tunnel endpoint.
C
IP-IP tunnels are stateful.
D
Tunnels add additional overhead to packet size.
Correct Answer:
B. Tunnel endpoints must have a valid route to the remote tunnel endpoint.
Explanation:
BD is correct because tunnel endpoints require valid routes to communicate effectively, and tunnels
inherently introduce overhead to packet sizes.
Justification for Correct Answers:
B. Tunnel endpoints must have a valid route to the remote tunnel endpoint.
This statement highlights the fundamental networking requirement that for any traffic to be transmitted
through a tunnel, routing information must be correctly configured. If a route to the remote endpoint does not
exist, packets will not be delivered, leading to communication failure.
D. Tunnels add additional overhead to packet size.
When encapsulating protocols, additional headers are introduced, increasing the payload size. This overhead
can affect overall network efficiency and performance, especially relevant in bandwidth-sensitive
applications.
Evaluation of Incorrect Options:
A. BFD cannot be used to monitor tunnels.
This statement is false; BFD (Bidirectional Forwarding Detection) can indeed be employed to monitor the
availability of tunnels. BFD operates effectively regardless of tunneling protocols and is often used in
conjunction with various tunneling technologies to ensure link stability.
C. IP-IP tunnels are stateful.
This is incorrect as IP-IP tunnels are stateless. They merely encapsulate packets within another IP header,
without maintaining session state or context. Stateful protocols, like those used in VPN technologies, involve
more complex interaction requiring session management.
References:
https://www.juniper.net/documentation/en_US/junos/topics/topic-map/ipv4-tunneling.html
https://www.cisco.com/c/en/us/support/docs/ip/bidirectional-forwarding-detection-bfd/79781-bfd-
overview.html
https://www.networkworld.com/article/3239542/understanding-ip-tunneling.html
Which statement is correct about IP-IP tunnels?
A
IP-IP tunnels only support encapsulating IP traffic.
B
IP-IP tunnels only support encapsulating non-IP traffic.
C
The TTL in the inner packet is decremented during transit to the tunnel endpoint.
D
There are 24 bytes of overhead with IP-IP encapsulation.
Correct Answer:
A. IP-IP tunnels only support encapsulating IP traffic.
Explanation:
A is correct because IP-IP tunnels are explicitly designed to encapsulate only IP packets.
IP-IP tunnels function by adding an additional IP header to the original IP packet, thus allowing for the
Evaluation of Other Options:
transport of IP traffic over disparate networks. This encapsulation enables functionalities such as the creation
of virtual private networks (VPNs) or routing across incompatible protocols, while strictly containing IP data
within the tunnel structure.
B. Incorrect: The assertion that IP-IP tunnels support only non-IP traffic is factually inaccurate; they are
specifically tailored for IP traffic encapsulation. This fundamentally misrepresents the role of IP-IP tunnels in
networking, as they facilitate the transmission of IP packets over various media.
C. Incorrect: The Time To Live (TTL) field in the inner packet is not decremented while traversing the tunnel;
rather, the TTL is decremented only when the packet exits the tunnel at the endpoint. This misinterpretation
can lead to misunderstanding of tunnel operation and packet lifespan management.
D. Incorrect: The claim of 24 bytes of overhead is inaccurate; the overhead for IP-IP tunneling is actually 20
bytes, consisting of the additional IP header that is added to encapsulate the original IP packet. This error
signifies a lack of precision regarding the encapsulation process and its implications for network
performance.
misrepresent their operation and structural details.
References:
In summary, A accurately reflects the functionality and purpose of IP-IP tunnels, while the other options
https://www.juniper.net/documentation/en_US/junos/topics/concept/ipip-tunnels.html
https://www.cisco.com/c/en/us/td/docs/ios/12_2/ip/configuration/guide/ip-ip-tunneling.html
https://www.networkworld.com/article/2693491/ipip-tunnels-in-ipv6.html
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