JNCIS-ENT Practice Test 4 — 25 Questions

Question 1

When configuring a Link Aggregation Group (LAG) on a Juniper switch, what is the naming convention used for the aggregated interface in the Junos CLI?

Accepted Answer

ae0, ae1, ae2, etc.. Junos uses the 'aeX' naming convention (Aggregated Ethernet) for LAG interfaces.

Answer

lag0, lag1, lag2, etc.

Answer

eth-trunk0, eth-trunk1, etc.

Answer

bond0, bond1, bond2, etc.

Question 2

Which CLI command displays detailed information about VRRP groups, including master router status, virtual IP addresses, and advertisement intervals on an EX series switch?

Accepted Answer

show vrrp detail. The 'show vrrp interface' or 'show vrrp detail' commands provide granular details regarding VRRP instance status.

Answer

show lacp vrrp-status

Answer

show spanning-tree vrrp

Answer

show chassis vrrp

Question 3

An engineer wants to configure a Link Aggregation Group (LAG) to load-balance traffic based on Layer 3 and Layer 4 header fields (source/destination IP and source/destination port) rather than just Layer 2 MAC addresses. How is this achieved in Junos?

Accepted Answer

Configure load-balance profiles under [edit forwarding-options hash-key] specifying inet protocols.. Junos allows configuring load-balancing profiles under the forwarding-options hierarchical level to include IP and port hash fields.

Answer

Enable LACP multi-chassis hashing under the chassis hierarchy.

Answer

Configure 'set interfaces ae0 load-balance layer-3-4' directly under the interface stanza.

Answer

Set the LACP periodic transmission interval to fast.

Question 4

An administrator configures a Link Aggregation Group (LAG) using LACP between two EX series switches. The link fails to aggregate, and the log shows 'LACP status: Expired'. What does the 'Expired' state indicate?

Accepted Answer

The local port has stopped receiving LACP packets from the remote peer within the timeout window.. The 'Expired' state in LACP means the local port has stopped receiving LACP packets from the remote peer within the expected timeout period.

Answer

The Virtual Chassis primary routing engine license has expired.

Answer

The Junos software license for aggregated Ethernet has expired.

Answer

The GRES synchronization timer has timed out.

Question 5

You are configuring Multi-Chassis Link Aggregation (MC-LAG) across two Juniper switches acting as separate control plane devices. Which protocol is used between the peer switches to synchronize state and ensure MAC address table consistency across the MC-LAG domain?

Accepted Answer

Inter-Chassis Control Protocol (ICCP). MC-LAG uses Inter-Chassis Control Protocol (ICCP) to coordinate state, consistency, and status between the two peer switches.

Answer

Open Shortest Path First (OSPF)

Answer

Graceful Routing Engine Switchover (GRES)

Answer

Virtual Router Redundancy Protocol (VRRP)

Question 6

Which CLI command verifies that OSPF Graceful Restart helper mode is enabled by default on a Juniper routing platform?

Accepted Answer

show ospf overview. Running 'show ospf neighbor detail' or 'show ospf overview' displays protocol-level graceful restart helper status.

Answer

show chassis ospf-status

Answer

show lacp ospf-helper

Answer

show vrrp ospf-restart

Question 7

Which operational command displays the configured member IDs, priorities, and roles in an EX Series Virtual Chassis?

Accepted Answer

show virtual-chassis. The 'show virtual-chassis' command displays member IDs, roles, priorities, and serial numbers.

Answer

show lacp aggregated-devices

Answer

show chassis alarms

Answer

show vrrp mastership

Question 8

Which TLV is used to carry IP prefixes in IS-IS?

Accepted Answer

TLV 128. TLV 128 and 135 are used for IP reachability information.

Answer

TLV 10

Answer

TLV 22

Answer

TLV 1

Question 9

An EX4300 Virtual Chassis has GRES enabled. During a primary Routing Engine failure, what happens to the backup Routing Engine?

Accepted Answer

The backup Routing Engine assumes the primary role without disrupting the forwarding plane or resetting packet forwarding tables.. With GRES enabled, the backup Routing Engine assumes the primary role seamlessly without resetting the forwarding plane or dropping data traffic.

Answer

The backup Routing Engine reboots both engines to synchronize firmware versions.

Answer

The Virtual Chassis splits into independent standalone switches.

Answer

All switch members in the Virtual Chassis are forced into factory default mode.

Question 10

An administrator is configuring VRRP on an EX4300 switch and wants to ensure that when the primary router recovers from a failure, it immediately reclaims the master role from the backup router. Which VRRP configuration parameter controls this behavior?

Accepted Answer

The preemption parameter (enabled by default), which allows a higher-priority router to preempt the current master.. Preemption is enabled by default in Junos VRRP, allowing a higher-priority router to take over when it comes back online.

Answer

The tracking decrement value set to zero.

Answer

The virtual-mac-address configuration statement.

Answer

The advertisement interval timer set to 1 millisecond.

Question 11

Which THREE conditions must be met to successfully execute an In-Service Software Upgrade (ISSU) on a dual-RE Juniper routing platform? (Choose three)

Accepted Answer

Both Routing Engines must be fully populated with identical hardware models and supported Junos images.. ISSU requires GRES enabled, NSR or graceful restart configured, and matching hardware/software paths.

Answer

All physical interfaces must be manually placed in a disabled state prior to upgrade.

Answer

VRRP preemption must be disabled on all routing interfaces.

Question 12

Which statement accurately describes port security MAC-limit behavior?

Accepted Answer

It restricts the maximum number of MAC addresses that can be learned on a secure interface.. Port security MAC-limit restricts the maximum number of MAC addresses learned on a secure interface.

Answer

It statically assigns all learned MAC addresses to the switch configuration file automatically.

Answer

It defines the maximum bandwidth a single MAC address can consume on a port.

Answer

It prevents MAC address spoofing by validating IP bindings against DHCP tables.

Question 13

When configuring Layer 2 firewall filters on an EX Series switch, which THREE statements are correct regarding filter structure and application? (Choose three)

Accepted Answer

They are configured under the 'family ethernet-switching' match criteria context.. Layer 2 filters use family ethernet-switching, can match on MAC addresses and EtherTypes, and are applied to interfaces or VLANs.

Answer

They are applied to logical Layer 3 routing interfaces (irb or vlan interfaces) using family inet.

Answer

They execute routing lookups prior to evaluating packet match conditions.

Question 14

You are troubleshooting a DIS election issue on a broadcast segment. What is the tie-breaker if the DIS priorities are equal?

Accepted Answer

The highest MAC address.. If DIS priorities are equal, the router with the highest Subnetwork Point of Attachment (SNPA) address (usually the MAC address) wins.

Answer

The lowest System ID.

Answer

The lowest MAC address.

Answer

The highest System ID.

Question 15

You need to redistribute OSPF routes into IS-IS. Where do you configure this?

Accepted Answer

Under the 'protocols isis export' hierarchy.. Redistribution is configured under the 'policy-options' and applied under 'protocols isis export'.

Answer

Under the OSPF configuration only.

Answer

It is not possible to redistribute OSPF into IS-IS.

Answer

Under the interface level.

Question 16

Which of the following are true about IS-IS Level-1 and Level-2 areas? (Choose TWO)

Accepted Answer

Level 2 is for connecting Level 1 areas.. Level 1 areas are for intra-area routing, while Level 2 areas connect multiple Level 1 areas.

Answer

Level 1 and Level 2 are the same thing.

Answer

Level 1 routers can communicate directly with routers in other areas.

Answer

Level 2 is for local interface management only.

Question 17

Which THREE conditions can cause a Virtual Chassis primary Routing Engine election or switchover to occur unexpectedly? (Choose three)

Accepted Answer

Manual modification of member priority values followed by a mastership switchover command or reboot.. Stacking cable failures, primary RE hardware crashes, or manual mastership changes/priority modifications trigger switchovers.

Answer

Configuring VRRP preemption on a VLAN interface.

Answer

A mismatch in LACP timeout intervals on aggregated Ethernet interfaces.

Question 18

In a multi-access network, which PDU is responsible for the DIS election?

Accepted Answer

IIH PDU. The IIH (IS-IS Hello) PDU contains the priority field used for DIS election on broadcast segments.

Answer

CSNP

Answer

LSP

Answer

PSNP

Question 19

How does a router determine its System ID?

Accepted Answer

It is manually configured.. The System ID is manually configured in the 'set protocols isis system-id' hierarchy.

Answer

It is learned via ARP.

Answer

It is automatically derived from the MAC address.

Answer

It is assigned by the DIS.

Question 20

Which TWO methods are used to connect switches in a Juniper EX Series Virtual Chassis? (Choose two)

Accepted Answer

Dedicated Virtual Chassis ports (VCPs) using specialized stacking cables.. EX Series switches use dedicated Virtual Chassis ports (VCPs) or uplink modules configured as VCPs using specialized cables.

Answer

Using standard serial console rollover cables for data and stacking traffic.

Answer

Running LACP over independent fiber strands between standalone switches.

Answer

Connecting standard access ports using unmanaged layer 2 Ethernet hubs.