JNCIS-ENT Protocol Independent Routing Practice Test 4 — 15 Questions

Question 1

Which statement best describes the behavior of a local route in Junos OS?

Accepted Answer

They represent IP addresses assigned directly to the router's local interfaces.. A local route in Junos OS represents the IP addresses assigned directly to the router's local interfaces. These routes are automatically installed in the routing table with a next-hop of the local interface and are used for traffic destined to the router itself. They are not learned from neighbors or manually configured as static routes.

Answer

They are static routes learned from neighbor routers via CDP.

Answer

They are manual loopback routes configured by network administrators.

Answer

They are generated automatically whenever a BGP session drops.

Question 2

An engineer is configuring static routes in Junos OS and wants to ensure high availability. Which TWO features can be implemented with static routes to achieve path redundancy? (Choose two)

Accepted Answer

Qualified next-hop with varying preference values. Option A (Qualified next-hop with varying preference values) is correct because Junos static routes support multiple qualified next-hops, each with its own preference; if the primary next-hop fails, the route with the next-lower preference becomes active, providing path redundancy. Option D (Recursive next-hop tracking via RPM or routing table lookups) is correct because a static route can resolve its next-hop recursively, and RPM (Real-time Performance Monitoring) probes or routing-table lookups can detect when the resolved next-hop becomes unreachable, allowing the route to be withdrawn or replaced. Option B (IGMP snooping) is a Layer 2 multicast optimization and does not provide static-route path redundancy. Option C (OSPF area stubbing) is a dynamic routing design technique for reducing LSAs, not a static-route feature. Option E (BGP AS-path prepending) is a BGP path-manipulation tool and cannot be applied to plain static routes.

Answer

IGMP snooping on static interfaces

Answer

OSPF area stubbing

Answer

BGP AS-path prepending on static routes

Question 3

When configuring load balancing in Junos OS, which THREE header fields can be included in the hashing algorithm to compute the ECMP path? (Choose three)

Accepted Answer

Layer 4 TCP/UDP port numbers. In Junos OS, the ECMP hashing algorithm used for load balancing can incorporate Layer 3 and Layer 4 header fields to distribute traffic across multiple equal-cost next hops. Option B (Layer 4 TCP/UDP port numbers) is correct because including transport-layer port numbers enables per-flow load balancing, so different sessions between the same hosts can take different paths. Option C (Source IP address) is correct because the source IP is a standard Layer 3 field used in the hash, allowing traffic from different sources to be spread across ECMP paths. Option E (Destination IP address) is correct because the destination IP is also a standard Layer 3 field in the hash, ensuring flows to different destinations are distributed. Option A (MAC address destination) is not included because ECMP hashing in Junos operates on Layer 3/Layer 4 fields, not on the destination MAC address. Option D (VLAN ID tagging bits) is not included because VLAN ID is a Layer 2 field and is not part of the ECMP hash computation in Junos OS.

Answer

MAC address destination

Answer

VLAN ID tagging bits

Question 4

When configuring Filter-Based Forwarding (FBF), which THREE components are absolutely mandatory for successful operation? (Choose three)

Accepted Answer

A firewall filter with 'then routing-instance ' action.. Option A is correct because FBF requires a firewall filter that matches traffic and uses the 'then routing-instance ' action to redirect matching packets into the alternate routing table. Option B is correct because that action must reference a routing instance of type 'forwarding' (or 'virtual-router'), which provides the separate routing table where the redirected traffic is resolved. Option C is correct because the filter must be applied as an input filter on the ingress interface so that packets are classified and redirected before the normal destination lookup occurs. Option D is incorrect because BGP multipath is a load-balancing feature and is not required for FBF to function. Option E is incorrect because RSVP-TE LSPs are an MPLS traffic-engineering mechanism and are unrelated to the mandatory FBF configuration components.

Answer

BGP multipath enabled across all core interfaces.

Answer

An RSVP-TE LSP tunnel configured between the routers.

Question 5

An administrator wants to configure load balancing across multiple static routes. Which THREE configuration elements are required to successfully implement ECMP load balancing for static routes in Junos? (Choose three)

Accepted Answer

Export of the load-balancing policy under 'routing-options forwarding-table export'.. To implement ECMP for static routes in Junos, you must first have multiple static routes to the same destination with equal preference and metric, because ECMP only installs paths of identical preference/metric into the forwarding table (option E). You then need a routing policy that contains the 'then load-balance' action, which tells Junos to install multiple next-hops for that destination rather than selecting a single best path (option C). Finally, that policy must be applied to the forwarding table via 'routing-options forwarding-table export', which is the mechanism that activates per-prefix load balancing for the routes (option B). BFD is not required for ECMP; it is an optional failure-detection mechanism (option A). A virtual-router routing instance is unrelated to ECMP and is used for routing-instance separation, not load balancing (option D).

Answer

BFD enabled on all static route next-hops.

Answer

A virtual-router routing instance wrapper.

Question 6

When configuring a routing instance of type 'virtual-router', which THREE characteristics apply? (Choose three)

Accepted Answer

Interfaces can be assigned directly to the virtual-router instance.. Option B is correct because a virtual-router routing instance in Junos is a true separate routing domain, so you assign physical or logical interfaces directly to it (for example, with 'set routing-instances interface ge-0/0/0.0'), and those interfaces then use the instance's own routing table. Option C is correct because a virtual-router instance runs its own routing protocol process and can run dynamic IGPs such as OSPF and IS-IS within that instance, independently of the master instance. Option E is correct because the defining feature of a virtual-router instance is that it maintains its own independent routing table (named .inet.0) that is separate from the main inet.0 table. Option A is not required, since a virtual-router instance is a pure Layer 3 routing separation and does not need MPLS label distribution protocols such as LDP or RSVP to function. Option D is false because Junos does not strictly prohibit route leaking between a virtual-router instance and inet.0; routes can be exchanged using rib-groups or instance-import/instance-export policies, so the statement is technically inaccurate.

Answer

It requires MPLS label distribution protocols to function.

Answer

Route leaking between virtual-router and inet.0 is strictly prohibited by Junos architecture.

Question 7

Which TWO attributes distinguish direct routes from static routes in Junos OS? (Choose two)

Accepted Answer

Direct routes represent subnets attached to active local interfaces.. Option B is correct because direct routes in Junos OS are automatically installed in the routing table for the subnets configured on active local interfaces, representing directly connected networks. Option E is correct because Junos assigns direct routes a default preference of 0, while static routes carry a default preference of 5, making direct routes more preferred when both exist for the same prefix. Option A is wrong because static routes are manually configured, not automatically created when an interface comes up; that behavior describes direct/interface routes. Option C is wrong because direct routes do not require manual configuration under routing-options; they are derived from interface addresses, whereas static routes are configured under routing-options. Option D is wrong because static routes can use recursive next-hops, resolving the next-hop through another route in the routing table.

Answer

Static routes are created automatically when an interface comes up.

Answer

Direct routes require manual IP address configuration under routing-options.

Answer

Static routes cannot be used with recursive next-hops.

Question 8

Which TWO parameters can be modified within a static route configuration to control path selection and backup behavior? (Choose two)

Accepted Answer

Qualified next-hop with custom preference. Option B is correct because in a static route you can specify a qualified next-hop and assign it a custom preference, allowing the router to prefer one next-hop over another for the same destination and thereby influence path selection and provide backup behavior. Option E is correct because the preference (administrative distance) value on a static route determines how it competes with routes from other protocols and with other static routes, so modifying it directly controls which route is installed and which serves as backup. Options A, C, and D are incorrect because MED, AS-path length, and local preference are BGP path attributes used in BGP route selection, not parameters that can be configured within a static route.

Answer

MED (Multi-Exit Discriminator)

Answer

AS-path length

Answer

Local preference attribute

Question 9

Which TWO statements accurately describe the behavior and characteristics of a routing instance of type 'forwarding'? (Choose two)

Accepted Answer

It is primarily used for filter-based forwarding applications.. Option D is correct because a 'forwarding' routing instance (also called a VRF-lite style instance) is designed for filter-based forwarding (FBF), where firewall filters on the ingress interface classify traffic and direct it into the instance's own routing table to control next-hop selection. Option E is correct because a forwarding-type instance maintains its own separate forwarding/routing table (RIB/FIB) but does not run any dynamic routing protocols such as OSPF, IS-IS, or BGP within it; routes are populated statically or via policy/filter actions. Option A is wrong because a forwarding instance does not automatically create a default route to the loopback interface; any default route must be configured manually or injected by policy. Option B is wrong because running independent OSPF and BGP instances is characteristic of a VRF-type routing instance, not a forwarding instance. Option C is wrong because MP-BGP for VPN label signaling is associated with VRF instances in MPLS L3VPN deployments, not with forwarding instances, which are local to the device and do not use VPN labels.

Answer

It automatically generates a default route pointing to the loopback interface.

Answer

It runs independent OSPF and BGP instances.

Answer

It requires MP-BGP for VPN label signaling.

Question 10

An engineer needs to configure a static IPv4 route on a Juniper Networks MX Series router pointing traffic destined for 192.168.100.0/24 to next-hop 10.0.0.1. Which configuration accomplishes this task?

Accepted Answer

set routing-options static route 192.168.100.0/24 next-hop 10.0.0.1. In Junos, static routes are configured under the [edit routing-options] hierarchy, not under protocols or interfaces. The correct syntax is 'set routing-options static route next-hop

', which installs the route into the inet.0 routing table for IPv4. This is the standard, documented method for defining a static IPv4 route on any Juniper device, including MX Series routers.

Answer

set routing-instances default static route 192.168.100.0/24 next-hop 10.0.0.1

Answer

set protocols static route 192.168.100.0/24 next-hop 10.0.0.1

Answer

set interfaces fxp0 unit 0 family inet static-route 192.168.100.0/24 next-hop 10.0.0.1

Question 11

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 12

An engineer configures an aggregate route for 172.16.0.0/16 on a Junos device. However, the aggregate route is not active in the routing table. What is the primary requirement for an aggregate route to become active?

Accepted Answer

At least one more-specific contributing route must exist in the routing table.. A Junos aggregate route becomes active only when at least one more-specific contributing route exists in the routing table. The aggregate is generated as a discard route (or with a configured next-hop) and is installed only if a longer-prefix route covered by the aggregate is present.

Answer

An explicit static route matching the aggregate prefix must be configured.

Answer

A discard policy must be explicitly defined under the aggregate route definition.

Answer

The aggregate route must be redistributed using BGP or OSPF.

Question 13

You are configuring a virtual router routing instance on a Juniper device to isolate traffic for a specific department. Which routing-instance type should you select?

Accepted Answer

virtual-router. A virtual-router routing instance creates a separate routing table (RIBs) and forwarding table (FIBs) for the instance, effectively giving the department its own logical router with independent interfaces, routing protocols, and policies. This is the correct type when you need full Layer 3 isolation with separate routing domains on the same physical device.

Answer

l2vpn

Answer

forwarding

Answer

no-forwarding

Question 14

You need to configure filter-based forwarding (FBF) to route traffic from a specific subnet (192.168.1.0/24) through an alternate next-hop gateway. Which components are required to implement this successfully?

Accepted Answer

A firewall filter with a routing-instance action, a custom routing instance, and application of the filter to the ingress interface.. Filter-based forwarding in Junos requires three elements working together: a stateless firewall filter that matches the traffic and applies a 'routing-instance' action, a custom routing instance (typically type forwarding) containing the alternate next-hop route, and the filter applied as an input filter on the ingress interface where the traffic arrives. The routing-instance action causes matched packets to be looked up in that instance's table instead of the main inet.0 table.

Answer

A static route pointing to the alternate gateway with a preference of 1.

Answer

An export routing policy with a load-balance action applied globally.

Answer

A firewall filter with a routing-instance action, a custom routing instance, and application of the filter to the egress interface.

Question 15

Which routing-instance type is specifically designed to support Layer 3 VPNs (L3VPNs) utilizing BGP as the-peering protocol and MP-BGP for VPN route distribution?

Accepted Answer

vrf. The vrf routing-instance type is specifically designed for Layer 3 VPNs (L3VPNs) that use BGP for peering and MP-BGP for VPN route distribution. It maintains a separate routing table (RIB) and forwarding table (FIB) per instance, enabling overlapping IP addresses across customers. VRF instances support BGP, OSPF, and other routing protocols, and they are the Junos equivalent of a VRF-lite or MPLS L3VPN VRF. The other types serve different purposes: virtual-router is for logical routers with separate routing tables but no VPN route-target support, forwarding is for filter-based forwarding, and VPLS is for Layer 2 VPNs.

Answer

virtual-router

Answer

forwarding

Answer

VPLS