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A network engineer configures two static routes on a Nokia 7750 SR to reach the same destination prefix 192.168.50.0/24 via two different next-hops, each with the default admin distance and equal preference values. Both next-hops are reachable and the interfaces are up. What behavior should the engineer expect in the route table and forwarding plane?
When two static routes to the same destination have identical preference (administrative distance) and both next-hops are valid and reachable, the 7750 SR installs both routes in the route table and uses Equal-Cost Multipath (ECMP) to load-balance traffic across them, provided ECMP is enabled and the max-ecmp-paths value allows it. The router does not arbitrarily discard one route based on next-hop IP address or configuration order; it only prefers routes with lower preference values or more specific prefixes.
An operator configures an IPv6 static route on a 7750 SR to a remote site reachable only through a single next-hop router. To ensure the static route is removed from the routing table quickly if that next-hop becomes unreachable due to a remote link failure not directly visible to the local router, which mechanism should be enabled on the static route?
BFD provides fast failure detection between the static route's next-hop and the local router, independent of interface link-down events, allowing the static route to be withdrawn quickly when the path becomes unusable, even for failures not directly observable at the local interface. IS-IS wide metrics relate to link-state metric encoding, route redistribution policies control which routes are advertised elsewhere, and graceful restart helper mode is unrelated to failure detection for static routes.
A service provider is designing a large IS-IS network and wants to limit the size of the link-state database on backbone routers while still allowing detailed topology information within each region. They decide to implement a two-level hierarchy with Level 1 areas connected through a Level 2 backbone. Which statement correctly describes how routing information flows in this design?
IS-IS hierarchy separates Level 1 (intra-area) topology detail from Level 2 (inter-area/backbone) topology. Level 1 routers have full visibility only within their own area and depend on Level 1/2 border routers to reach other areas, commonly via an attached-bit-triggered default route or via leaked Level 2 prefixes into Level 1. This reduces database size on Level 1 routers while the backbone (Level 2) carries inter-area reachability. The other options misstate how information is scoped between levels.
During troubleshooting of an IS-IS multi-area network, an engineer notices that a specific customer prefix learned in Level 1 Area 1 is not reachable from a router in Level 1 Area 2, even though both areas connect to the same Level 2 backbone and default routes are being learned correctly. The engineer wants routers in Area 2 to gain visibility of this specific Level 1 prefix rather than relying solely on the default route. Which IS-IS feature should be configured to accomplish this?
Route leaking allows specific prefixes to be advertised from Level 1 up into Level 2 by the border router in Area 1, and then optionally from Level 2 back down into Level 1 in Area 2 by that area's border router, using an up/down bit to prevent routing loops. This gives routers in Area 2 visibility of the specific prefix instead of relying only on the default route toward Level 2. Wide metrics affect metric range, not prefix visibility; a static route is not a scalable IS-IS-native solution; LSP refresh interval is unrelated to prefix leaking.
A network architect wants to reduce traffic loss during a link or node failure in an IS-IS network without waiting for the SPF recalculation to converge, by having routers pre-compute an alternate next-hop for critical prefixes. Which IS-IS-related feature on the Nokia 7750 SR is designed specifically to address this requirement?
Loop-Free Alternate (LFA) and IP Fast Reroute pre-compute a backup next-hop for each primary next-hop for prefixes, based on the SPF topology, so that traffic can be rerouted within milliseconds after a failure is detected, before full SPF reconvergence completes. Mesh-group flooding reduction limits unnecessary LSP flooding in dense topologies but does not provide backup paths. HMAC-MD5 authentication secures IS-IS PDUs but is unrelated to failure recovery speed. The overload bit signals that a router should not be used for transit but does not provide fast reroute capability.
40 questions covering all exam domains, starting from $20
Exam domains verified against: Official Nokia 4A0-112 exam guide, last checked September 2026.
Master routing table population, ECMP behavior, and route redistribution using policies. Understand Nokia 7750 SR architecture and Layer-3 interface configuration.
Compare static route characteristics, failure detection options, and IPv6 static route configuration. Understand when static routing is appropriate in network design.
Sample question from this domain above: Q1
Distinguish between distance vector and link-state protocols. Learn shortest path first algorithm and link-state protocol message flooding and optimizations.
Sample question from this domain above: Q2
Master IS-IS hierarchy, message types, adjacency formation, and database synchronization. Configure route leaking, summarization, external prefix advertising, and LFA fast reroute.
Common questions about the exam itself
