JNCIP-ENT BGP Advanced Practice Test 2 — 15 Questions

Question 1

An administrator implements BGP entropy labels and path load balancing on a Junos routing platform. During packet forwarding for a BGP-learned IPv4 prefix with multiple equal-cost paths, how does Junos determine the output interface when hash-based load balancing is active?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

Hashing selected packet header fields to compute an index into the set of resolved BGP next hops.. Junos hashes packet header fields (such as source/destination IP, ports, and optional hash keys or entropy labels) to select a specific path from the available BGP multipaths.

Answer

Using the lowest MED value among the multipath entries for every packet transmission.

Answer

Consulting the BGP Route Reflector cluster list to determine the optimal egress port.

Answer

Round-robin packet scheduling across all available BGP next hops regardless of flow headers.

Question 2

Which command allows an administrator to view the active BGP routes along with their associated communities on a Junos device?

Accepted Answer

show route protocol bgp extensive. The 'show route protocol bgp' command with the 'extensive' modifier displays detailed path attributes including BGP communities.

Answer

show bgp group summary

Answer

show bgp neighbor extensive

Answer

show route forwarding-table protocol bgp

Question 3

An enterprise network uses BGP communities to tag routes at regional branch offices. Headquarters needs to strip these specific communities from routes before advertising them to external transit providers. Which Junos routing policy action accomplishes this?

Accepted Answer

community delete target_community. Using the 'community delete' action within a routing policy removes specified communities from routes matching the policy.

Answer

community set target_community

Answer

as-path-remove target_community

Answer

metric set 0

Question 4

A network engineer is configuring a Junos routing device to use BGP Prefix-Independent Convergence (PIC) edge for faster failover. What is the fundamental mechanism that enables BGP PIC to achieve sub-second convergence upon primary path failure?

Accepted Answer

It pre-installs a backup loop-free alternate (LFA) next hop in the forwarding plane for rapid hardware switching.. BGP PIC pre-computes a backup loop-free alternate next hop and installs it in the forwarding table alongside the primary next hop, allowing hardware-based failover.

Answer

It bypasses the routing table entirely and queries the BGP route reflector directly upon failure.

Answer

It forces the IGP to recalculate shortest paths immediately using fast-reroute without BGP participation.

Answer

It increases the BGP keepalive and hold timers to prevent session tearing during link flaps.

Question 5

A Junos router receives a BGP route containing multiple extended and large communities. The administrator writes a routing policy to filter routes based on large communities. Which format is used to define a large community in Junos policy-options?

Accepted Answer

large-community:global_administrator:local_data1:local_data2. Large communities in Junos policy-options are defined using the format large-community:global_administrator:local_data1:local_data2.

Answer

as-number:identifier

Answer

target:as-number:identifier

Answer

ipv4-address:identifier

Question 6

An engineer is troubleshooting a BGP route reflection topology where a non-client IBGP peer sends a route to a route reflector. Will the route reflector reflect this route to other non-client IBGP peers?

Accepted Answer

No, routes received from a non-client peer are only reflected to client peers, not to other non-client peers.. A route reflector reflects routes from clients to clients, clients to non-clients, and non-clients to clients, but it does NOT reflect routes received from a non-client to other non-client peers.

Answer

Yes, all routes received by a route reflector are reflected to all peers regardless of client status.

Answer

No, route reflectors never reflect routes received from any IBGP peer.

Answer

Yes, provided the routes contain the same Cluster ID as the receiving non-client peer.

Question 7

Which Junos configuration hierarchy is used to define a BGP peer group to simplify neighbor configurations?

Accepted Answer

protocols bgp group <group-name>. BGP peer groups and neighbor settings are configured under the 'protocols bgp group' hierarchy in Junos.

Answer

routing-options autonomous-system

Answer

interfaces <interface-name> unit 0 family inet bgp

Answer

policy-options community

Question 8

An administrator configures BGP dampening on a Junos router to mitigate the impact of flapping routes. When a route exceeds the reuse threshold after being suppressed, what happens to its penalty value?

Accepted Answer

The penalty value continues to decay exponentially until it drops to zero.. When a dampened route's penalty decays below the reuse threshold, the route becomes eligible again, and its penalty continues to decay exponentially toward zero.

Answer

The penalty value is locked at the reuse threshold value indefinitely.

Answer

The penalty value is doubled to discourage further flapping.

Answer

The penalty value is instantly reset to zero.

Question 9

A BGP routing policy on a Junos router uses an 'as-path' regular expression '^[0-9]+$' in a match condition. Which routes will this regular expression match?

Accepted Answer

Routes whose AS path contains exactly one AS number ( originated from a directly connected neighboring AS ).. The regex '^[0-9]+$' matches an AS path that consists of exactly one autonomous system number (from the beginning to the end of the path string).

Answer

Routes that contain internal confederation segments.

Answer

Routes whose AS path starts with local AS 65000 and has multiple hops.

Answer

Any route originating from any AS path of any length.

Question 10

Which TWO actions can be performed using Junos BGP routing policies? (Choose two)

Accepted Answer

Modifying the local preference attribute of incoming IBGP routes.. Junos routing policies can filter routes and modify path attributes such as local preference or MED.

Answer

Dynamically altering the BGP session TCP handshake port numbers.

Answer

Adjusting the BGP keepalive timer values dynamically via policy match actions.

Answer

Manually assigning physical interface MTU sizes for BGP sessions.

Question 11

An operator configures BGP attribute value manipulation using a Junos routing policy. Specifically, the policy uses 'as-path-action prepend' combined with community matching. When is this outbound policy evaluated relative to BGP route selection?

Accepted Answer

When advertising routes to a BGP peer, after the best path has been chosen.. Outbound export policies are evaluated when advertising routes to peers, after the best path has been selected locally.

Answer

During the initial import processing from EBGP peers before next-hop resolution.

Answer

Before the best path is selected, affecting the local routing table calculation.

Answer

During the route selection algorithm right after MED comparison.

Question 12

Which THREE conditions must be met for a Junos routing device to consider two BGP paths as valid candidates for multipath load balancing when standard multipath is configured? (Choose three)

Accepted Answer

The next hops must be resolvable via active routing table entries.. Standard BGP multipath in Junos requires matching AS path lengths, local preferences, and valid IGP next-hop resolution, among other consistent attributes.

Answer

The router IDs of the advertising peers must be identical.

Answer

The route advertisement intervals must be synchronized across all peers.

Question 13

When configuring a BGP confederation, how are external peers outside the confederation affected by the internal sub-AS structure?

Accepted Answer

They see only the top-level confederation AS number in the AS path attribute.. External peers outside the confederation see only the top-level confederation AS number, as internal member AS numbers are stripped when exiting the confederation boundary.

Answer

They require explicit configuration of every member AS in their own EBGP import filters.

Answer

They see all member AS numbers prepended individually in the AS path.

Answer

They reject all updates originating from a confederation due to AS path validation failures.

Question 14

An administrator is troubleshooting BGP route reflector operations in a Junos environment. Which TWO statements regarding route reflection behavior and loop prevention are correct? (Choose two)

Accepted Answer

A route reflector ignores any advertised route that contains its own local Cluster ID in the Cluster List.. Route reflectors use Originator ID to prevent loops from clients and Cluster Lists to prevent loops between cluster route reflectors.

Answer

Route reflectors change the BGP next hop to their own IP address when reflecting routes to clients by default.

Answer

Route reflectors remove the AS_PATH attribute when reflecting routes to internal non-client peers.

Answer

Route reflectors modify the Local Preference attribute to zero for all reflected routes.

Question 15

Which TWO attributes are considered transitive BGP path attributes? (Choose two)

Accepted Answer

COMMUNITY. AS_PATH and COMMUNITY are standard well-known transitive and optional transitive attributes respectively, whereas LOCAL_PREF is well-known discretionary (non-transitive across AS).

Answer

MED (Multi-Exit Discriminator)

Answer

ORIGINATOR_ID

Answer

LOCAL_PREF