JNCIS-ENT Timed Practice Test 2 — 10 Questions

Question 1

Which TWO BGP attributes are strictly internal to an Autonomous System and are never advertised to external eBGP peers? (Choose two)

Accepted Answer

ORIGINATOR_ID. Local Preference and MED (by default, unless propagated) or internal-only attributes like cluster list are restricted. Specifically, Local Preference is never sent to eBGP peers.

Answer

NEXT_HOP

Answer

ORIGIN

Answer

AS_PATH

Question 2

A Junos router receives four identical routes via BGP. Reviewing the routing table, path selection picked route 3. Route 1 has a lower MED, Route 2 has a higher Local Preference, Route 4 is from an eBGP peer while Route 3 is iBGP. Assuming standard default path selection, why was Route 3 chosen over Route 4?

Accepted Answer

Junos prefers iBGP paths over eBGP paths during the tie-breaking steps.. In Junos BGP path selection, after comparing local preference, AS path length, origin type, and MED, Junos prefers internal (iBGP) paths over external (eBGP) paths, provided all other tie-breakers are equal.

Answer

Route 3 had a lower router ID than Route 4.

Answer

Route 3 had a lower MED value.

Answer

Route 3 was received from a peer with a lower peer IP address.

Question 3

You need to configure authentication for a BGP peering session on a Junos device to prevent spoofing attacks. Where is the MD5 authentication key configured?

Accepted Answer

protocols bgp group name authentication-key. BGP MD5 authentication keys are configured under the specific neighbor or group definition using the authentication-key statement.

Answer

firewall family inet filter bgp-auth

Answer

system authentication-algorithm md5

Answer

routing-options md5-key

Question 4

Which level is enabled by default in Junos when configuring IS-IS on an interface?

Accepted Answer

Level 1 and Level 2. By default, interfaces in Junos IS-IS are enabled for both Level 1 and Level 2.

Answer

None

Answer

Level 2 only

Answer

Level 1 only

Question 5

How does an IS-IS router identify the DIS in its hello packets?

Accepted Answer

By the router's System ID followed by a non-zero pseudonode ID.. The DIS is identified by the System ID and a pseudonode number (the 7th byte of the LSP ID).

Answer

By a special flag in the header.

Answer

By the area address.

Answer

By the MAC address only.

Question 6

When evaluating the BGP path selection algorithm on a Junos device, which THREE attributes are evaluated BEFORE the router considers the IGP metric to the BGP next hop? (Choose three)

Accepted Answer

Multi-Exit Discriminator (MED). The path selection order in Junos is: 1. Local Preference, 2. AS Path length, 3. Origin type, 4. MED, 5. iBGP over eBGP, 6. IGP metric to next hop. Therefore, local preference, AS path length, and MED are evaluated before the IGP metric.

Answer

IGP metric to next hop

Answer

Router ID

Question 7

You are verifying BGP Graceful Restart helper mode on a Juniper router. A peering router restarts its control plane. What output or verification command confirms that your router is acting as a Graceful Restart helper for the peer?

Accepted Answer

Run 'show bgp neighbor' and verify that the 'Graceful Restart' capability is advertised and received, and observe the restart state flags.. Using 'show bgp neighbor' displays the graceful restart capabilities negotiated and whether the peer is currently in restart state.

Answer

Run 'show chassis routing-engine' to verify that the remote neighbor has updated its local RE priority.

Answer

Run 'show lacp statistics ae0' to see if LACP packets are being suppressed during restart.

Answer

Run 'show vrrp summary' to check if the BGP neighbor has assumed the master VRRP role.

Question 8

A network engineer wants to verify IS-IS link-state database entries, specifically checking for TLVs that carry extended IP reachability information with wide metrics. Which Junos operational command should be used?

Accepted Answer

show isis database detail. To view the IS-IS link-state database with detailed TLV and metric information on Junos devices, the command 'show isis database detail' is used.

Answer

show isis adjacency extensive

Answer

show ospf database

Answer

show route protocols isis

Question 9

An engineer configures iBGP peering between two routers in the same AS. Route reflection is not used. The engineer notices that routes learned from an eBGP peer by Router A are not being advertised by Router A to Router B (its iBGP peer). Why is this happening?

Accepted Answer

BGP split-horizon prevents a router from advertising routes learned from one iBGP peer to another iBGP peer.. BGP split-horizon rule dictates that routes learned from an iBGP peer cannot be advertised to another iBGP peer to prevent routing loops. (Note: standard iBGP to iBGP split horizon applies; to share routes, full mesh, route reflectors, or confederations must be used).

Answer

External routes cannot be carried over iBGP without encapsulation.

Answer

The Local Preference attribute defaults to 0 for iBGP routes, causing them to be suppressed.

Answer

iBGP peers require the 'multipath' statement to be configured before any route exchange can occur.

Question 10

An engineer is preparing to perform an In-Service Software Upgrade (ISSU) on a pair of dual-RE MX240 routers. Which condition must be met to ensure the ISSU succeeds without dropping traffic?

Accepted Answer

Graceful Route Engine Switchover (GRES) and Nonstop Active Routing (NSR) must be enabled and functioning.. ISSU requires specific hardware compatibility (matching RE models, line card types), GRES and NSR configured and operating, and a supported Junos image path.

Answer

The backup Routing Engine must be physically removed from the chassis during the upgrade.

Answer

All physical interfaces must be manually disabled prior to issuing the request system software in-service command.

Answer

All routing protocols must be migrated from OSPF to IS-IS before starting ISSU.