JNCIS-SP Juniper Specialist Service Provider

In IS-IS, what is the primary distinction between a Level 1 (L1) router and a Level 2 (L2) router?

• AL1 routers route within an area; L2 routers route between areas and form the IS-IS backbo…
• BL1 routers use OSPF-compatible LSAs; L2 routers use NLPID-tagged PDUs
• CL1 routers only advertise IPv6 prefixes; L2 routers only advertise IPv4 prefixes
• DL1 routers require manual neighbor discovery; L2 routers use automatic adjacency

Which IS-IS PDU type is used to describe the local link-state database and is flooded throughout the IS-IS domain?

• ALink State PDU (LSP)
• BHello PDU (IIH)
• CComplete Sequence Number PDU (CSNP)
• DPartial Sequence Number PDU (PSNP)

What is the purpose of IS-IS wide metrics, and what is the maximum metric value they support?

• AWide metrics extend the metric range to 16,777,214 to support traffic engineering and MPL…
• BWide metrics allow IS-IS to advertise up to 65,535 prefixes per LSP
• CWide metrics enable IS-IS to support more than 1,024 neighbors per router
• DWide metrics replace TLV 2 with TLV 22 and limit the metric to 255

On a Junos router, which IS-IS TLV carries extended IP reachability information used for wide metrics?

• ATLV 135
• BTLV 128
• CTLV 2
• DTLV 22

Which IS-IS TLV carries the router's NET (Network Entity Title) and system ID?

• ATLV 240 (P2P Adjacency State)
• BTLV 1 (Area Addresses)
• CTLV 10 (Authentication)
• DTLV 22 (Extended IS Reachability)

In OSPF, which LSA type is generated by an ABR and describes routes that are external to an area but internal to the OSPF domain?

• AType 3 (Summary LSA)
• BType 4 (ASBR Summary LSA)
• CType 5 (AS External LSA)
• DType 7 (NSSA External LSA)

What is the key difference between an OSPF stub area and a totally stubby area?

• AA stub area blocks Type 5 LSAs; a totally stubby area blocks Type 3, 4, and 5 LSAs — repl…
• BA stub area blocks Type 3 LSAs; a totally stubby area blocks only Type 5 LSAs
• CA totally stubby area is used only on Cisco equipment; Junos uses stub areas exclusively
• DA stub area injects a default route via Type 7; a totally stubby area uses Type 5 for the…

In OSPF, what is an NSSA (Not-So-Stubby Area) and which LSA type does it introduce?

• AAn NSSA blocks external Type 5 LSAs from the backbone but allows an ASBR inside the NSSA…
• BAn NSSA blocks all LSA types except Type 1 and Type 2, using Type 7 to carry backbone rou…
• CAn NSSA allows Type 5 external LSAs to flood freely but limits Type 3 to a summary default
• DAn NSSA uses Type 8 LSAs to replace both Type 5 and Type 7 at the ABR

What is the purpose of an OSPF virtual link?

• ATo connect a partitioned area to the backbone (Area 0) through a non-backbone transit area
• BTo carry OSPF routing information over an MPLS LSP between two PE routers
• CTo establish an OSPF neighbor relationship across a BGP peering session
• DTo redistribute IS-IS routes into OSPF without an ASBR

Which OSPF authentication method provides the strongest security for OSPF neighbor relationships on Junos?

• AMD5 authentication using a shared key configured under the OSPF area or interface
• BSimple (plain-text) password authentication
• CIPsec AH authentication applied to OSPF packets
• DNo authentication, relying on network segmentation alone

In BGP, what is the difference between iBGP and eBGP?

• AiBGP peers are within the same AS; eBGP peers are in different autonomous systems
• BiBGP peers use TCP port 179 directly; eBGP peers use UDP for lightweight updates
• CiBGP increases the MED on all routes; eBGP uses local-preference instead
• DiBGP is used for IPv4 only; eBGP supports multi-protocol extensions

Why is a full iBGP mesh required in a network without route reflectors or confederations?

• AiBGP does not re-advertise routes learned from one iBGP peer to another iBGP peer, so eac…
• BA full mesh ensures that iBGP uses the lowest-latency path for route updates
• CiBGP requires a full mesh because it uses multicast for update delivery
• DJunos enforces a full mesh requirement at the configuration level to prevent loops

What is the primary function of a BGP route reflector (RR)?

• ATo re-advertise iBGP routes to other iBGP peers, eliminating the need for a full iBGP mesh
• BTo translate eBGP routes from one AS into another AS's iBGP domain
• CTo aggregate BGP prefixes before advertising them to the internet
• DTo perform AS path prepending on all inbound eBGP routes

In BGP path selection on Junos, which attribute is compared first after filtering routes with an invalid next-hop?

• ALocal preference (highest wins)
• BAS path length (shortest wins)
• CMED (lowest wins)
• DOrigin code (IGP preferred over EGP)

What does BGP local-preference control, and what is its default value on Junos?

• AIt influences exit point selection for traffic leaving the AS; Junos default is 100
• BIt influences which AS-path is preferred for routes entering the AS; Junos default is 0
• CIt sets the MED value advertised to eBGP neighbors; Junos default is 100
• DIt controls the weight of a specific BGP session; Junos default is 32768

What is the BGP MED (Multi-Exit Discriminator) attribute used for?

• ATo suggest to a neighboring AS which entry point to use when multiple links connect the t…
• BTo set the preferred exit path within the local AS for outbound traffic
• CTo mark routes that should be filtered before being redistributed into the IGP
• DTo signal the number of AS hops between the originating router and the BGP peer

In Junos policy language, which action causes the current term to reject a route and stop evaluating further terms?

• Areject
• Bnext term
• Cnext policy
• Ddeny

What is the effect of the `then accept` action at the end of a Junos routing policy term?

• AThe matched route is accepted and no further terms or policies in the chain are evaluated
• BThe matched route is accepted and evaluation continues to the next term
• CThe matched route is placed in the routing table as active without affecting further poli…
• DThe matched route is accepted and then sent to the next policy in the export chain

In Junos, what is a BGP community and how is it typically used?

• AA BGP community is an optional transitive attribute (32-bit value) used to tag routes for…
• BA BGP community is a mandatory BGP attribute that sets the local-preference for all prefi…
• CA BGP community is a Junos-specific feature that identifies routes learned from route ref…
• DA BGP community is an iBGP-only attribute used to identify which cluster a route belongs…

What does the BGP well-known community `no-export` (0xFFFFFF01) instruct a BGP speaker to do?

• ADo not advertise the route to any eBGP peers — keep it within the AS (or confederation)
• BDo not advertise the route to any peers, including iBGP peers
• CDo not advertise the route to route reflectors within the local cluster
• DRemove all communities from the route before advertising it to eBGP peers

What is a BGP confederation, and what problem does it solve?

• AA confederation divides a large AS into sub-ASes to reduce the iBGP full-mesh requirement…
• BA confederation aggregates multiple customer ASes under a single provider AS number
• CA confederation is an iBGP cluster where all routers peer through a single route reflector
• DA confederation is a Junos feature that merges two OSPF areas into a single BGP domain

On Junos, which routing table stores MPLS label-switched paths and is used by LDP and RSVP for label forwarding?

• Ainet.3
• Binet.0
• Cmpls.0
• Dbgp.l3vpn.0

What is the fundamental difference between LDP and RSVP-TE in MPLS label distribution?

• ALDP distributes labels based on IGP topology (hop-by-hop) without traffic engineering; RS…
• BLDP uses TCP for label distribution; RSVP-TE uses UDP to minimize overhead
• CLDP is used only for L2VPN services; RSVP-TE is used exclusively for L3VPN
• DLDP builds LSPs only for IPv6 prefixes; RSVP-TE handles IPv4 LSPs

In RSVP-TE, what is the purpose of the ERO (Explicit Route Object)?

• AThe ERO specifies the explicit sequence of hops (IP addresses or AS numbers) the LSP must…
• BThe ERO records the actual path taken by RSVP-TE Path messages after they are forwarded
• CThe ERO carries bandwidth reservation requests from the ingress PE to the egress PE
• DThe ERO identifies which MPLS labels have been allocated along the LSP path

What is MPLS Fast Reroute (FRR), and which RSVP-TE mechanism is most commonly used for it?

• AFRR provides sub-50ms traffic recovery by pre-establishing bypass LSPs around potential f…
• BFRR is an LDP feature that automatically reroutes traffic around failed links using IGP r…
• CFRR is a Junos proprietary feature that duplicates MPLS packets on both primary and backu…
• DFRR uses BGP PIC (Prefix Independent Convergence) to pre-install backup routes in the FIB

In an MPLS L3VPN (RFC 4364), what is the purpose of the Route Distinguisher (RD)?

• AThe RD makes VPN-IPv4 routes globally unique in the MP-BGP table by prepending a unique 8…
• BThe RD controls which VRFs import and export routes between PE routers
• CThe RD is the MPLS label used to identify customer traffic in the provider network
• DThe RD maps a VPN customer's AS number to the service provider's AS number

In MPLS L3VPN, what is the function of the Route Target (RT) extended community?

• AThe RT controls VPN route import and export: VRFs export routes tagged with specific RTs…
• BThe RT uniquely identifies each VPN prefix in the MP-BGP table to prevent address overlap
• CThe RT specifies the MPLS label value that will be assigned to VPN traffic on the provide…
• DThe RT is the BGP next-hop address used by PE routers to reach the CE router

In Junos L3VPN, which routing table holds VPNv4 routes received from remote PE routers via MP-BGP?

• Abgp.l3vpn.0
• Binet.3
• Cinet.0
• Dmpls.0

In an MPLS L3VPN, what does 'two-label stack' (penultimate hop popping and VPN label) mean during label forwarding?

• AThe transport label (outer) routes the packet across the provider backbone via the LSP, a…
• BThe first label identifies the customer, and the second label identifies the provider's c…
• CThe two labels are always identical — one is used for load balancing and the other for ba…
• DThe outer label is the customer's CE IP address encoded as a label, and the inner is the…

Which Junos operational command displays the contents of the MPLS label switching table on a PE router?

• Ashow route table mpls.0
• Bshow bgp summary
• Cshow mpls lsp
• Dshow route table inet.3

What does the Junos command `show isis adjacency` display?

• AThe current IS-IS neighbor adjacencies including interface, system ID, adjacency state (U…
• BThe complete IS-IS link-state database (LSDB) for the local router
• CThe IS-IS SPF calculation results and computed shortest paths
• DThe IS-IS route table entries installed in inet.0

What information does `show ospf neighbor` provide on a Junos router?

• AIt shows OSPF neighbors including neighbor ID, priority, state (Full, 2-Way, Exchange), d…
• BIt shows all OSPF LSAs in the link-state database along with sequence numbers
• CIt shows the OSPF routing table with costs and next-hops
• DIt shows OSPF interface configuration including hello and dead intervals

Which Junos command verifies that a BGP session is established and shows the number of received prefixes?

• Ashow bgp summary
• Bshow route table bgp.l3vpn.0
• Cshow bgp group
• Dshow route advertising-protocol bgp <neighbor>

On Junos, what is the function of the `commit` command, and how does it differ from `commit confirmed`?

• A`commit` immediately applies the candidate configuration to the active configuration; `co…
• B`commit` saves the configuration to a file without applying it; `commit confirmed` applie…
• C`commit` applies only OSPF and BGP changes; `commit confirmed` applies changes to all pro…
• D`commit` requires all users to log off before applying; `commit confirmed` allows other u…

How many previous configurations does Junos store, and what command restores a prior configuration?

• AJunos stores up to 50 previous configurations; `rollback <number>` loads a prior configur…
• BJunos stores up to 5 previous configurations; `restore config <number>` immediately appli…
• CJunos stores unlimited configurations in /var/db/config; `load override` applies any arch…
• DJunos stores 10 previous configurations; `commit rollback` immediately reverts without a…

In Junos, what does the `show route` command display by default?

• AAll active routes from inet.0 (the main IPv4 unicast routing table) including the protoco…
• BOnly routes learned via BGP from all routing tables
• COnly directly connected and static routes from inet.0
• DAll routes from all routing tables including inet.0, mpls.0, and bgp.l3vpn.0

In PIM Sparse Mode (PIM-SM), what is the role of the Rendezvous Point (RP)?

• AThe RP is the meeting point for multicast sources and receivers — sources register with t…
• BThe RP is the router closest to the multicast source that forwards traffic directly to al…
• CThe RP performs IGMP queries to discover multicast group membership on all LAN segments
• DThe RP is the last-hop router that delivers multicast traffic to receivers in the group

What is IGMP (Internet Group Management Protocol) used for in a multicast network?

• AIGMP is used by hosts to join and leave IP multicast groups, and by routers to discover w…
• BIGMP is the protocol used between PIM routers to build the multicast distribution tree
• CIGMP is the protocol used by the RP to register multicast sources in PIM-SM
• DIGMP is used to carry multicast routing updates between routers in the SP backbone

In Junos, what is a routing instance, and how is it used in L3VPN?

• AA routing instance is an independent set of routing tables and policies; in L3VPN, each c…
• BA routing instance is a backup routing table that takes effect only when the primary rout…
• CA routing instance is a Junos feature that allows OSPF and IS-IS to run simultaneously in…
• DA routing instance is used exclusively for BGP and contains only VPNv4 routes from remote…

What is the Junos CoS (Class of Service) scheduler's role in an SP network?

• AThe scheduler defines how bandwidth is allocated and queued for each traffic class on an…
• BThe scheduler controls which prefixes are accepted from BGP peers based on traffic class…
• CThe scheduler assigns DSCP values to incoming packets based on their source IP address
• DThe scheduler manages MPLS label allocation for different traffic classes on the provider…

In Junos CoS, which field in an IP packet is used to classify traffic into forwarding classes?

• AThe DSCP (Differentiated Services Code Point) field in the IP header, or the 802.1p bits…
• BThe IP TTL field, which is decremented at each hop and used to assign priority
• CThe TCP source port number, which identifies the application and assigns the traffic class
• DThe IP protocol number (TCP=6, UDP=17), which determines the scheduling queue

What does the Junos `show route advertising-protocol bgp <neighbor-address>` command display?

• AThe routes that the local router is currently advertising to the specified BGP neighbor
• BThe routes received from the specified BGP neighbor before policy is applied
• CAll BGP routes in inet.0 regardless of whether they are being advertised
• DThe BGP session state and hold timer for the specified neighbor

What is the purpose of Junos automation with SLAX/XSLT and op scripts in an SP environment?

• AOp scripts automate operational tasks (show commands, triggered actions) that can be run…
• BOp scripts replace routing policy and configure BGP neighbors automatically without admin…
• CSLAX/XSLT scripts are used exclusively for modifying the Junos configuration database dur…
• DOp scripts provide a Python interface to reprogram the ASIC forwarding tables directly

In IS-IS, how are IS-IS adjacencies formed on a point-to-point (P2P) link?

• ATwo routers exchange IS-IS Hello (IIH) PDUs; on P2P links, the three-way handshake mechan…
• BP2P IS-IS adjacencies require a Designated IS (DIS) election before forming
• CP2P IS-IS adjacencies are formed using OSPF-style DBD (Database Description) exchange
• DOn P2P links, IS-IS routers do not form adjacencies — they exchange LSPs directly using L…

In IS-IS on a broadcast (multi-access) network, what is the role of the Designated Intermediate System (DIS)?

• AThe DIS generates the Pseudonode LSP representing the LAN, reduces flooding overhead by a…
• BThe DIS is the router with the highest system ID that becomes the only router allowed to…
• CThe DIS is elected permanently and cannot be preempted, similar to OSPF DR/BDR behavior
• DThe DIS performs SPF calculations on behalf of all L1 routers in the area

What is the default administrative distance (preference) for OSPF internal routes on Junos?

• A10
• B100
• C170
• D200