JNCIS-ENT Practice Test 2 — 10 Questions

Question 1

Which TWO options represent valid benefits of configuring Link Aggregation Groups (LAG)? (Choose two)

Accepted Answer

Increased aggregate bandwidth between connected networking devices.. Option A is correct because a Link Aggregation Group bundles multiple physical interfaces into a single logical link, so the combined throughput of the member links provides increased aggregate bandwidth between the connected devices. Option D is correct because LAG monitors member link health and, if one physical member link fails, traffic is automatically redistributed across the remaining active links, providing redundancy and failover without losing the logical interface. Option B is incorrect because BGP peer state synchronization is handled by BGP itself (e.g., via TCP sessions and route reflectors), not by LAG. Option C is incorrect because Junos OS upgrades are performed through software management procedures, not through link aggregation. Option E is incorrect because LAG does not eliminate the need for Spanning Tree Protocol in all cases; STP may still be required to prevent loops in topologies with redundant paths outside the LAG.

Answer

Synchronization of BGP routing daemon state between separate routers.

Answer

Automatic upgrade of Junos OS across peer devices.

Answer

Elimination of the need for Spanning Tree Protocol across all VLANs.

Question 2

A network administrator needs to modify the Local Preference path attribute for all routes received from a specific external BGP peer using a routing policy on Junos. Under which configuration hierarchy should the routing policy be applied?

Accepted Answer

protocols bgp group neighbor import. To modify Local Preference for routes received from a specific eBGP peer, the routing policy must be applied as an import policy on that neighbor or group under 'protocols bgp group neighbor import '. Import policies are evaluated on inbound updates, which is where Local Preference is typically set for eBGP-learned routes.

Answer

policy-options policy-statement term then export

Answer

routing-options rib inet.0 static

Answer

protocols ospf area

Question 3

You want to ensure that a static route is only installed in the routing table when a specific tracked object or ping test succeeds. Which Junos feature should you pair with the static route?

Accepted Answer

RPM (Real-time Performance Monitoring) with static route tracking. RPM (Real-time Performance Monitoring) in Junos allows you to configure probes that periodically test reachability of a target (e.g., via ICMP ping) and track the results. When you associate a static route with an RPM probe using the `track` option, the route is only installed in the routing table if the probe succeeds. This provides conditional route installation based on real-time performance monitoring, ensuring the static route is active only when the tracked object is reachable.

Answer

OSPF sham-links

Answer

Keepalive timers on static routes

Answer

BFD synchronized static routes

Question 4

What is the primary function of a Junos tunnel interface when used in conjunction with routing protocols?

Accepted Answer

To provide a virtual point-to-point layer 3 link for routing protocol adjacencies across an untrusted or disjointed transport network.. A Junos tunnel interface provides a virtual point-to-point Layer 3 link that can carry routing protocol adjacencies across a transport network that may not support multicast or is disjointed. This allows routing protocols like OSPF or BGP to form neighbors over the tunnel, treating it as a direct connection.

Answer

To act as a physical layer 2 bridge for VLAN extension without IP addresses.

Answer

To encrypt all transit traffic by default using hardware-based AES-256.

Answer

To replace physical interfaces for standard local area network connections.

Question 5

When implementing Layer 2 firewall filters on an EX Series switch, which packet characteristic can be matched in a filter term?

Accepted Answer

Source MAC address. Layer 2 firewall filters in Junos can match fields such as source MAC address, destination MAC address, VLAN ID, and EtherType.

Answer

Destination IP address

Answer

ICMP type code

Answer

TCP port number

Question 6

Which OSPF packet type is responsible for discovering neighbors and maintaining adjacencies on a Junos device?

Accepted Answer

Hello (Type 1). OSPF Hello packets (Type 1) are responsible for neighbor discovery and maintaining adjacencies. They are sent periodically on OSPF-enabled interfaces, and they carry parameters like router ID, area ID, hello/dead intervals, and neighbor lists. If Hellos stop arriving within the dead interval, the adjacency is torn down.

Answer

Link-State Update (Type 4)

Answer

Link-State Request (Type 3)

Answer

Database Description (Type 2)

Question 7

When calculating OSPF path costs in a network containing high-speed links (such as 10Gbps and 40Gbps interfaces), what default reference bandwidth does Junos use, and what configuration adjustment is typically required to differentiate costs accurately?

Accepted Answer

100 Mbps default; reference bandwidth must be increased to accurately cost high-speed links.. Junos OSPF uses a default reference bandwidth of 100 Mbps, so any interface at 100 Mbps or faster gets a cost of 1, making 1G, 10G, and 40G links indistinguishable. To differentiate high-speed links, the reference bandwidth must be increased (e.g., to 10G or higher) using the reference-bandwidth statement under protocols ospf.

Answer

100 Gbps default; reference bandwidth must be decreased for legacy interfaces.

Answer

10 Gbps default; no adjustment is needed for modern networks.

Answer

1 Gbps default; interfaces above 1 Gbps are automatically assigned fractional costs.

Question 8

Which THREE criteria are evaluated by Junos when electing the primary Routing Engine in an EX Series Virtual Chassis? (Choose three)

Accepted Answer

Switch uptime or boot order sequence if priorities are identical.. Junos elects the primary Routing Engine in an EX Series Virtual Chassis using a defined set of criteria, and option D is correct because the configured routing-engine mastership priority (set with 'set virtual-chassis member X mastership-priority') is the first and most significant factor—the member with the highest priority wins. Option A is correct because when mastership priorities are equal, the switch with the longer uptime (earlier boot order) becomes primary, ensuring a stable and deterministic election. Option C is correct because if both priority and uptime are identical, the base MAC address of the switch is used as a final deterministic tie-breaker, with the lower MAC address typically winning. Option B is incorrect because VRRP router ID on VLAN 1 is a Layer 3 redundancy mechanism unrelated to Virtual Chassis RE election. Option E is incorrect because the number of active LACP links is not a criterion in the Virtual Chassis primary election process.

Answer

The VRRP router ID configured on VLAN 1.

Answer

The number of active LACP links connected to member 0.

Question 9

Which TWO statements are correct regarding the operation of MSTP instance 0 (CIST)? (Choose two.)

Accepted Answer

It handles any VLANs that are not explicitly mapped to another user-defined MST instance.. Option A is correct because MSTP instance 0, the CIST, carries all VLANs that are not explicitly mapped to a user-defined MST instance (MSTI); these unmapped VLANs default to the CIST and are forwarded along the CIST topology. Option D is correct because instance 0 is by definition the Common and Internal Spanning Tree (CIST), which provides the single spanning-tree topology that interconnects all MST regions and also interoperates with external SST/RSTP regions. The unmarked options are wrong: B is false because the CIST does interact with external RSTP switches by treating each external region as a virtual bridge and running RSTP-based interoperation at region boundaries; C is false because MSTP uses the standard 802.1D hop-count limit of 20 (not 1) for the CIST; and E is false because root protection (root guard) can be configured on CIST/instance-0 ports to prevent them from becoming root ports.

Answer

It operates independently without any interaction with external RSTP switches.

Answer

It is limited strictly to a maximum hop count of 1.

Answer

It prohibits the use of root protection on instance 0 ports.

Question 10

An administrator configures a static route with a next-hop that points to an indirect (recursive) address. What condition must be met for this static route to become active in the inet.0 routing table?

Accepted Answer

A more direct route to the next-hop IP must already exist and be active in inet.0.. For a static route with an indirect (recursive) next-hop to become active in inet.0, the router must already have an active route to that next-hop IP in inet.0. This is the definition of recursive resolution: the next-hop must be reachable via another route in the same routing table. Without this, the static route remains hidden.

Answer

The static route preference must be set lower than 1.

Answer

The next-hop IP must be directly connected to a physical interface on the local router.

Answer

BGP multipath must be enabled under routing-options.