Cisco 300-510 SPRI Service Provider Advanced Routing Practice Exam

Correct: A. A stub area blocks Type 5 external LSAs while still accepting Type 3 inter-area summaries, with a default route injected for external destinations. OSPF special area types are an explicit SPRI objective.

Why not the others: the backbone (B) carries all LSA types and cannot be a stub; a totally stubby area (C) blocks Type 3 summaries as well, which is the distinction being tested; and a transit area (D) describes a role in carrying traffic between areas, not an LSA-filtering type.

Correct: B. Route reflectors relax the iBGP full-mesh requirement by reflecting routes between clients, scaling the AS without changing its structure. Confederations solve the same problem but by dividing the AS into sub-ASes — which the question rules out.

Why not the others: confederations (A) require exactly the sub-AS split excluded here; static routes (C) do not carry BGP path attributes; and disabling iBGP (D) breaks internal reachability propagation.

Correct: C. A Level 1-2 router keeps separate L1 and L2 link-state databases and acts as the boundary between an area and the IS-IS backbone — the direct analogue of an OSPF area border router. IS-IS multilevel operation is an explicit objective.

Why not the others: an L1-only router (A) sees only its own area, an L2-only router (B) participates only in the backbone, and a pseudonode (D) is a logical construct representing a broadcast segment, not a router role.

Correct: B. Multicast Source Discovery Protocol peers rendezvous points across domains so each learns of active sources elsewhere via Source-Active messages — the standard interdomain multicast mechanism, and a named SPRI objective.

Why not the others: IGMP (A) signals host group membership on a local segment; OSPF (C) is a unicast IGP; and LDP (D) distributes MPLS labels.

Correct: C. The RP is the root of the shared tree: sources register with it and receivers join toward it, after which the network may switch to a shortest-path tree. That explicit-join, shared-root model is what makes sparse mode sparse.

Why not the others: flooding by default (A) describes dense mode; address assignment (B) is DHCP’s job; and the RP complements rather than replaces unicast routing (D), which still provides the RPF check.

Correct: A. RPL is IOS XR’s policy framework, using structured blocks, sets, and conditional logic in place of classic route-map syntax. Implementing the Routing Policy Language is an explicit SPRI objective, which is why IOS XR familiarity is recommended.

Why not the others: a DHCP relay agent (B) forwards address requests, spanning tree (C) prevents Layer 2 loops, and NTP (D) synchronises clocks — none define routing policy.

Correct: D. Route tagging marks routes as they are redistributed so the other boundary can identify and deny them, breaking the feedback loop. Combined with metric control and filtering, it is the standard fix for mutual redistribution.

Why not the others: MTU (A) is unrelated to route propagation, disabling the IGPs (B) removes routing altogether, and adding redistribution points (C) increases rather than reduces the loop risk.

Correct: B. The LFIB holds the incoming-to-outgoing label mappings and the associated forwarding actions, so it is where label-swapping behaviour is verified. The LIB, by contrast, stores all labels learned from LDP peers rather than the forwarding decisions in use.

Why not the others: the ARP cache (A) maps IP to MAC, the DHCP binding table (C) tracks address leases, and the MAC address table (D) is Layer 2 switching — none carry MPLS label forwarding state.

Correct: C. Segment routing carries the path as an ordered list of segments in the packet header, so only the ingress node needs path state — midpoint routers hold no per-LSP state. That state reduction is the core scalability argument against RSVP-TE.

Why not the others: segment routing still requires IP addressing (A) and depends on an IGP to distribute segment identifiers (B), and it operates in IP/MPLS networks rather than being confined to Layer 2 switches (D).

Correct: D. TI-LFA precomputes a backup path to the post-convergence route and uses the segment list to steer traffic onto it, delivering sub-50ms protection without the topology restrictions that limit classic LFA. Implementing TI-LFA is an explicit SPRI objective.

Why not the others: address assignment (A) is DHCP, encryption (B) is a security function such as MACsec or IPsec, and update compression (C) is not what TI-LFA does.