1. A table holds S 10.1.5.0/24 [1/0] and O 10.1.5.0/24 [110/20] for the identical prefix. Which installs, and which test decided it? The OSPF route, decided by metric The static route, decided by administrative distance The static route, decided by longest-prefix match Both, load-shared
Check answer 2. Now the OSPF route is a /26 covering the destination and the static is a /24. Which wins? The static, because AD 1 still beats AD 110 The OSPF /26, because a longer prefix wins before AD is considered Neither — mixed sources cannot overlap Whichever was installed first
Check answer 3. A remote LAN is missing from R1's table. Why is show ip ospf neighbor the right first command rather than show ip route? It is faster to type It splits the problem in two: no FULL neighbour means an adjacency fault, a FULL neighbour means a local route-blocking error It shows the routing table as well The routing table is unreliable during convergence
Check answer 4. Router X shows a neighbour stuck in ExStart. Router Y shows no neighbour at all. What are the two most likely causes? Both are MTU mismatches X is an MTU mismatch; Y is an adjacency-blocking mismatch such as an area or subnet mismatch X is an area mismatch; Y is an MTU mismatch Both are duplicate Router IDs
Check answer 5. You raise auto-cost reference-bandwidth on R1 only. What is the consequence across the area? Nothing — the setting is local and harmless R1 and the other routers compute different costs for the same links and can disagree on the best path OSPF adjacencies drop immediately All routes are recalculated with the new value automatically
Check answer 6. OSPF elects the DR by highest priority then highest Router ID. How does that compare with the STP root election from Week 3? They are identical — both are highest-wins They are opposite — STP elects the lowest Bridge ID, OSPF elects the highest priority and RID STP is highest-wins and OSPF is lowest-wins Neither uses an election; both are configured manually
Check answer 7. A colleague blames a missing OSPF route on passive-interface being set on that LAN. Are they right? Yes — passive-interface withdraws the network from OSPF No — a passive interface still advertises its connected subnet; it only stops Hellos Yes, but only on broadcast segments Only if the interface is also shut down
Check answer 8. R1 has a static default to its ISP and runs default-information originate. What do other OSPF routers install, and what happens if R1's static is removed? O*E2 0.0.0.0/0; it is withdrawn when R1 loses its own default S* 0.0.0.0/0; it persists regardless O 0.0.0.0/0; it becomes a connected route Nothing is advertised until always is added
Check answer 9. With OSPF running correctly in both directions, is the missing-return-route fault from Lesson 2 still possible? Yes, exactly as before — OSPF changes nothing It is far less likely, because a working adjacency advertises reachability both ways rather than relying on hand-configured statics No — OSPF makes routing bidirectional by definition Only if passive-interface is configured
Check answer 10. In HSRP, why does the standby router take over the virtual MAC as well as the virtual IP on failover? To satisfy spanning tree So the host's cached ARP entry stays valid and nothing on the host has to change Because the virtual IP alone cannot be routed To force a DHCP renewal on every host
Check answer 11. R1 has priority 110 and R2 has 90. R1 fails, R2 becomes active, then R1 recovers. Who is active, and what single setting decides it? R1 always reclaims, because its priority is higher R2 stays active unless R1 has standby preempt configured Both become active until the group is reset R1 reclaims after the dead timer expires
Check answer 12. What redundancy problem does HSRP solve that OSPF does not, even in a fully converged area? Redundant paths between routers A redundant default gateway for end hosts, which run no routing protocol Faster convergence after a link failure Load balancing across equal-cost paths
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