Routing Fundamentals

JN0-106 · 23 questions

• A rural fiber cooperative's edge router learns three different paths toward the regional data center's /24 subnet: one from a directly connected interface, one from a manually entered static route, and one from OSPF. Which structure does Junos consult first to decide which of these candidate paths gets used to actually forward subscriber traffic?
• After Junos on a subscriber-aggregation router chooses the single best path to a village's DSL access switch, that path needs to reach the Packet Forwarding Engine so subscriber traffic actually moves. Which table receives just that one active, forwarding-ready path?
• Two different sources — a manually configured static route and OSPF — both offer the aggregation router at a rural exchange point a path to the same downstream /24. Junos has to pick one as active. What general rule governs that choice when multiple protocols offer a route to the identical destination?
• A co-op's edge router has three routes sitting in inet.0 for the exact same prefix: one from a directly connected interface, one static route an engineer configured, and one learned via OSPF. Assuming none of the preference values were manually changed from their Junos defaults, which of these three is generally the most trusted and becomes the active route?
• An engineer runs a route lookup on a co-op's core router and sees two entries for the same downstream /24, but only one of them is marked as the route Junos is actually using to forward subscriber traffic right now. What is that in-use route called?
• A NOC technician at a regional ISP notices a static route to a backup POP still listed under show route even though OSPF is currently supplying the preferred, active path to that same destination. What best describes the static route's current status?
• A small telecom cooperative has one router with a single upstream transit provider and no dynamic routing protocol running toward that provider. The network engineer wants to guarantee a specific, predictable path out of the network without relying on any protocol adjacency. Which routing mechanism directly fits this need?
• A rural ISP wants traffic destined for a retired subscriber block to be dropped immediately at the aggregation router without sending any notification back to the sender, to avoid generating extra traffic toward customers who are still probing that old range. Which static route next-hop option produces this silent-drop behavior?
• An engineer configures a static route for a decommissioned subnet at a co-op's head-end and wants the router to actively notify any sender that the destination is unreachable, rather than dropping packets without a trace. Which next-hop keyword accomplishes this?
• A network engineer at a regional ISP is deciding whether to use discard or reject for a static route covering an aggregate summary block that includes some currently unassigned subscriber subnets. Silent discard risks packets vanishing without any diagnostic clue if a legitimate customer is accidentally caught in the summary. Which factor should most directly drive the choice between discard and reject here?
• A co-op wants a static route to its regional data center to normally use the primary fiber path, but automatically fail over to a secondary microwave link if the primary next-hop becomes unusable, without running a dynamic routing protocol. Which static route feature is designed for assigning a distinct preference value to each of several next-hops for the same destination?
• A cooperative configures its regional data center route with a primary next-hop toward its main transit provider and a qualified next-hop toward a secondary transit provider carrying a higher (less preferred) preference value. What common name describes this overall static routing design, where the backup path only becomes active if the primary disappears from the routing table?
• A router at a small cooperative's head-end needs a single routing table entry that matches any destination not covered by a more specific route, so subscriber traffic bound for the wider internet has somewhere to go. Which route accomplishes this?
• An engineer configures a static route on a co-op's aggregation router, but the next-hop IP address typed in isn't on any subnet directly attached to that router, it's only reachable through another route already sitting in the table. What must happen before this static route can actually be used to forward traffic?
• A network engineer explains that Junos can maintain more than one independent routing table on the same device, each with its own set of routes, entirely separate from the default inet.0 table. What is this general capability called at an introductory level?
• A regional cooperative offers wholesale broadband service to several smaller downstream providers over the same core routers, and wants each downstream provider's routes kept completely separate from the co-op's own internal backbone routes on the same device. Which routing concept most directly supports this kind of separation?
• A network engineer describes a dynamic routing protocol category where each router periodically advertises its entire routing table, along with a simple metric like hop count, to its directly connected neighbors, without any router building a full map of the network topology. What category of protocol is being described?
• An engineer at a regional carrier explains that instead of trusting secondhand summaries from neighbors, every router in this protocol's area independently floods information about its own directly connected links, so each router ends up building its own complete map of the topology before computing the best paths. Which protocol category does this describe?
• A regional ISP runs one routing protocol among its own routers inside its single autonomous system, and a different protocol to exchange reachability information with its separate upstream transit provider's autonomous system. Which pair of terms correctly labels these two protocol roles?
• A regional ISP is growing quickly, adding new aggregation sites and backup links every quarter, and the network engineer is tired of manually updating static routes across a dozen routers every time the topology changes. What is the main advantage of adopting a dynamic routing protocol in this situation?
• A small rural cooperative operates a single router with exactly one upstream transit connection and no plans to add a second one. The engineer is deciding whether to run a dynamic routing protocol toward that upstream or simply configure a static default route. Which factor most strongly favors the static route in this specific case?
• A co-op's edge router faces the public internet, and the engineer wants it to drop any incoming packet whose source address doesn't have a matching route pointing back out the same interface it arrived on, catching spoofed traffic using the router's own routing table rather than a separately written filter. Which mechanism does this?
• A subscriber-facing interface on a co-op's aggregation router goes physically down. The router had a directly connected route to that interface's subnet, which had been the active route in the forwarding table. What happens to that route once the interface is down?