JNCIS-ENT Practice Test 2 — 25 Questions

Question 1

During troubleshooting of a flapping BGP session, you notice BGP Notification messages being sent. Which BGP message type is responsible for tearing down a session due to an error condition?

Accepted Answer

NOTIFICATION. The Notification message is sent when an error is detected, causing the BGP connection to close immediately.

Answer

KEEPALIVE

Answer

UPDATE

Answer

OPEN

Question 2

What is the primary function of the BGP OPEN message?

Accepted Answer

To establish a peering session and negotiate capabilities such as ASNs and timers.. The OPEN message is the first message sent after a TCP connection is established, used to negotiate BGP parameters such as ASN, hold time, and router ID.

Answer

To advertise reachability and path attributes for network prefixes.

Answer

To maintain the connection state and verify liveliness at regular intervals.

Answer

To signal fatal errors and immediately terminate the BGP session.

Question 3

An administrator needs to verify the exact BGP timers negotiated with an eBGP peer on a Junos device. Which operational command should be used?

Accepted Answer

show bgp neighbor. The 'show bgp neighbor' command provides detailed information about a BGP neighbor session, including negotiated hold time, keepalive interval, state, and message statistics.

Answer

show ospf neighbor

Answer

show bgp summary

Answer

show route advertising-protocol bgp

Question 4

An engineer configures a Virtual Chassis using EX4300 switches. To ensure member IDs are assigned consistently even if physical positions change, how should the administrator provision the member IDs?

Accepted Answer

Pre-provision member serial numbers to specific member IDs using the 'request virtual-chassis assign' or configuration statements.. Junos allows pre-provisioning Virtual Chassis member serial numbers to specific member IDs to maintain predictable topologies.

Answer

Rely on automatic plug-and-play assignment, which permanently locks member IDs based on initial boot order.

Answer

Disable GRES so that member IDs do not synchronize across the stack.

Answer

Configure the MAC address of each switch under the [edit chassis vrrp] hierarchy.

Question 5

Which THREE statements accurately describe the behavior and configuration of VRRP tracking on Junos devices? (Choose three)

Accepted Answer

If the decremented priority falls below the backup router's priority, mastership transitions to the backup router.. VRRP tracking lowers priority when interfaces fail, can monitor multiple interfaces, and allows backup routers to take over.

Answer

Tracking forces the tracked interface to shut down permanently when a failure occurs.

Answer

Tracking automatically disables GRES on the routing engine.

Question 6

Which THREE attributes are optional transitive BGP path attributes? (Choose three)

Accepted Answer

AS4_PATH. Optional transitive attributes include COMMUNITY, AGGREGATOR, and AS4_PATH. MED is optional non-transitive. Local Pref and AS_PATH are well-known.

Answer

MED

Answer

LOCAL_PREF

Question 7

Which THREE statements describe the role and function of the BGP Router ID? (Choose three)

Accepted Answer

It is exchanged during the BGP OPEN message negotiation phase.. The Router ID is a 32-bit identifier chosen during startup, used as a tie-breaker in BGP path selection, and included in OPEN messages.

Answer

It automatically replaces the AS_PATH attribute if missing.

Answer

It must be identical across all routers within the same Autonomous System.

Question 8

A network operator needs to peer two routers in different Autonomous Systems that are not directly connected. Security policy mandates that TTL security checks be bypassed. Which command satisfies this requirement for the BGP session?

Accepted Answer

set protocols bgp group ebgp multihop ttl 255. TTL security can be bypassed or adjusted using multihop or adjusting the ttl value directly.

Answer

set protocols bgp group ebgp hold-time 180

Answer

set protocols bgp group ebgp passive

Answer

set protocols bgp group ebgp disable-ttl-drop

Question 9

Which THREE statements regarding Juniper Virtual Chassis architecture and master election are correct? (Choose three)

Accepted Answer

Pre-provisioning member serial numbers ensures consistent member ID assignments regardless of boot order.. Virtual Chassis mastership is determined by priority, preemption can cause takeovers, and pre-provisioning serial numbers ensures stable member IDs.

Answer

Split-brain detection automatically shuts down all core routing protocols without administrator intervention.

Answer

Virtual Chassis ports (VCPs) require LACP active mode configuration on every stacking cable.

Question 10

While examining a BGP routing table, you notice a route with an ORIGIN attribute set to 'Incomplete'. What does this indicate about the origin of the route?

Accepted Answer

The route was injected into BGP via redistribution (e.g., from static or IGP).. BGP origin types are IGP (0), EGP (1), and Incomplete (2). Incomplete means the route origin is unknown, typically redistributed from an IGP or static route.

Answer

The route was learned via eBGP from an unknown AS.

Answer

The BGP update packet was corrupted in transit.

Answer

The route is an aggregate route without specific components.

Question 11

An administrator is troubleshooting a BGP peering session that is stuck in the Connect or Active state. Which THREE common causes could explain this issue? (Choose three)

Accepted Answer

TCP port 179 is blocked by a firewall filter.. A session stuck in Active/Connect means the TCP session cannot be established. Causes include incorrect peer IP/AS, firewall blocking port 179, or missing multihop/TTL settings.

Answer

Route reflection client parameters are misconfigured.

Answer

Incorrect peer AS number configured in the OPEN message parameters.

Question 12

An administrator configures a BGP policy to reject routes with an AS_PATH containing a specific AS number. Which match condition in a Junos routing policy is used to evaluate the AS_PATH?

Accepted Answer

as-path. In Junos, the as-path match condition evaluates routes against a defined as-path regular expression.

Answer

pref

Answer

metric

Answer

community

Question 13

You notice that an iBGP peer is not advertising routes it learned from an eBGP peer to other iBGP peers. What architectural rule explains this behavior?

Accepted Answer

iBGP split-horizon rule. The iBGP split-horizon rule states that routes learned via iBGP cannot be advertised to other iBGP peers to prevent routing loops.

Answer

eBGP TTL security check

Answer

MED restriction across AS boundaries

Answer

AS_PATH loop detection

Question 14

A network engineer configures an eBGP session on a Junos device and notices that routes learned from the external peer are not being installed in the routing table or advertised to other peers. What is the default behavior regarding eBGP route propagation and next-hop resolution on Junos OS?

Accepted Answer

The local router does not set the next-hop to itself for eBGP peers, but for iBGP peers the next-hop must be resolvable via an IGP.. By default, eBGP does not change the next-hop address when advertising routes to external peers, but when advertising to iBGP peers, it preserves the next-hop unless 'next-hop-self' is configured. However, for routes to be active, the next-hop must be resolvable in the routing table.

Answer

Junos automatically drops all eBGP routes unless an explicit import policy is applied allowing them.

Answer

eBGP routes require the 'as-override' statement to be active in the forwarding table.

Answer

eBGP automatically changes the next-hop to the local router interface for all advertised routes.

Question 15

You need to ensure that BGP sessions fail over within sub-second intervals if a link degrades or goes down. Which protocol should you integrate with BGP on your Junos router?

Accepted Answer

BFD (Bidirectional Forwarding Detection). BFD (Bidirectional Forwarding Detection) provides fast failure detection that can trigger BGP session teardown within milliseconds.

Answer

STP (Spanning Tree Protocol)

Answer

LDP (Label Distribution Protocol)

Answer

OSPF

Question 16

Which TCP port is used by BGP to establish communication between peers?

Accepted Answer

TCP 179. BGP operates over TCP port 179.

Answer

UDP 520

Answer

TCP 80

Answer

TCP 500

Question 17

Which THREE path attributes are classified as 'well-known mandatory'? (Choose three)

Accepted Answer

NEXT_HOP. The well-known mandatory attributes in BGP are ORIGIN, AS_PATH, and NEXT_HOP. Local Preference is well-known discretionary, and MED is optional non-transitive.

Answer

MED

Answer

LOCAL_PREF

Question 18

Which THREE statements are true regarding OSPF Graceful Restart helper mode on Juniper routers? (Choose three)

Accepted Answer

It helps prevent unnecessary SPF recalculations across the network during transient control plane restarts.. Helper mode allows routers to maintain routing tables while neighbors restart, suppressing routing churn and dropping adjacencies prematurely.

Answer

It forces the restarting router to immediately drop all data forwarding traffic.

Answer

It requires manual configuration of VRRP tracking on all loopback interfaces.

Question 19

A BGP speaker receives an UPDATE message containing a malformed attribute. According to BGP specifications, which action does the receiving router take?

Accepted Answer

Send a NOTIFICATION message and terminate the BGP session.. A malformed attribute or critical error triggers a NOTIFICATION message with an appropriate error code, followed by session teardown.

Answer

Strip the attribute and propagate the route to iBGP peers.

Answer

Send an UPDATE message requesting retransmission.

Answer

Silently ignore the attribute and install the route.

Question 20

How do you configure an interface to be point-to-point when using IS-IS?

Accepted Answer

set protocols isis interface point-to-point. You use the 'set protocols isis interface point-to-point' command to force point-to-point mode.

Answer

set protocols isis interface-type point-to-point

Answer

set interfaces <name> unit 0 family iso point-to-point

Answer

set protocols isis link-type p2p