JNCIS-ENT Practice Test 10 — 10 Questions

Question 1

Which statement is true regarding the behavior of storm control when the traffic rate exceeds the configured threshold?

Accepted Answer

Excess traffic exceeding the threshold is dropped by the switch hardware.. When storm control thresholds are exceeded, Junos drops the excess traffic matching the storm control criteria until the rate drops below the threshold.

Answer

Traffic is rate-shaped and buffered in the output queue until congestion clears.

Answer

The interface is immediately shut down and placed in an error-disabled state.

Answer

The switch sends SNMP traps and forwards the traffic with a low-priority CoS marking.

Question 2

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 3

You are reviewing the configuration of an EX Series switch and notice that interface ge-0/0/15 is configured with 'interface-mode access' but has no explicit 'vlan members' statement defined. Which VLAN does the interface default to?

Accepted Answer

VLAN 1 (default VLAN). On Juniper EX Series switches, when an interface is configured with 'interface-mode access' and no explicit 'vlan members' statement is present, the interface automatically becomes a member of the default VLAN, which is VLAN ID 1. This default VLAN is created by the system and is named 'default'. The interface will forward untagged traffic into VLAN 1, allowing connectivity without additional configuration.

Answer

VLAN 0 (null VLAN)

Answer

The port remains shut down until a VLAN is explicitly assigned.

Answer

It drops all traffic until a VLAN membership is added.

Question 4

Which OSPF area is mandatory in any multi-area OSPF routing architecture?

Accepted Answer

Area 0 (Backbone Area). Area 0, also known as the backbone area, is mandatory in multi-area OSPF architectures. All other areas must connect directly or via virtual links to Area 0.

Answer

Area 1

Answer

A totally stubby area

Answer

An NSSA area

Question 5

You have configured multiple static routes to the same destination with different preference values. When does Junos install a static route into the forwarding table (FIB)?

Accepted Answer

Only the static route with the lowest preference value is installed into the FIB.. Junos uses preference (administrative distance) to rank routes from the same or different protocols; the route with the lowest preference value is preferred and installed into the forwarding table (FIB). If multiple static routes to the same destination have equal preference, all can be installed for ECMP, but when preferences differ, only the lowest-preference route wins. This mirrors the standard 'lower is better' convention used by Junos for route preference.

Answer

Only the static route with the highest preference value is installed into the FIB.

Answer

All static routes are installed into the FIB, and traffic is automatically load-balanced across them.

Answer

All valid static routes are installed into the FIB regardless of preference values.

Question 6

During OSPF database synchronization, two Junos routers exchange Database Description (DBD) packets. One router repeatedly sends DBD packets with the master/slave bit set incorrectly or encounters sequence number mismatches, causing the adjacency to loop in the Exchange state. Which OSPF packet type is immediately sent by a router to request missing link-state information once the ExStart/Exchange transition completes?

Accepted Answer

Link-State Request (Type 3). Once the ExStart/Exchange transition completes, a router sends Link-State Request (Type 3) packets to request specific link-state advertisements (LSAs) that are missing or outdated. This occurs after the Database Description exchange, where routers identify which LSAs they need. The Link-State Request is used to request the full LSA from the neighbor.

Answer

Hello (Type 1)

Answer

Database Description (Type 2)

Answer

Link-State Update (Type 4)

Question 7

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.. Option A is correct because a Juniper EX Series Virtual Chassis can be formed by cabling the dedicated Virtual Chassis ports (VCPs) on the switches with the specialized stacking cables designed for those ports, which carry the inter-switch control and data traffic. Option C is also correct because on supported EX platforms you can convert standard network uplink ports (for example 10G or 40G interfaces) into Virtual Chassis ports via configuration, allowing a Virtual Chassis to be built without dedicated VCP hardware. Option B is wrong because serial console rollover cables are for out-of-band management access, not for carrying Virtual Chassis data or stacking traffic. Option D is wrong because LACP is a link-aggregation protocol for standard Ethernet links and does not create or operate a Virtual Chassis fabric. Option E is wrong because unmanaged Layer 2 hubs on access ports cannot provide the required VCP connectivity or the control-plane communication a Virtual Chassis needs.

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.

Question 8

What happens if you have an LSP with an expired lifetime?

Accepted Answer

The LSP is removed from the LSDB.. When an LSP's remaining lifetime reaches zero, it is purged from the database after a short period.

Answer

The router immediately crashes.

Answer

The LSP is flooded to all neighbors.

Answer

The router re-elects a new DIS.

Question 9

Which configuration command enables Graceful Routing Engine Switchover (GRES) globally on a Juniper routing platform?

Accepted Answer

set chassis redundancy graceful-switchover. GRES is enabled under the [edit chassis redundancy graceful-switchover] hierarchy in Junos.

Answer

set routing-options gres enable

Answer

set interfaces redundancy gres

Answer

set system graceful-restart

Question 10

Which feature is required to be enabled on an access switch to populate the DHCP snooping database binding table with legitimate client IP-to-MAC address mappings?

Accepted Answer

DHCP Snooping. DHCP snooping must be enabled on the access switch to build the DHCP snooping binding database, which maps client IP addresses to MAC addresses, VLANs, and interfaces. This database is populated by snooping DHCP ACK messages as clients obtain leases. Without DHCP snooping enabled, the binding table remains empty, and features like Dynamic ARP Inspection and IP Source Guard cannot function.

Answer

Dynamic ARP Inspection

Answer

IP Source Guard

Answer

Port Security MAC-Limit