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Question 470
A routed Gi0/1 links two OSPF routers. Both endpoints have correct area 0, IP addresses, authentication and Hello timers, but R1 inadvertently configures `passive-interface Gi0/1`. Which action restores Hello exchange on this actual peering link?
- Increase the OSPF reference bandwidth to 1 Tb/s
- Remove unintended passive-interface on the peering link
- Add a static default route via the neighbor
- Configure passive-interface on the other router too
Explanation
Correct Answer
B:An OSPF passive interface may still advertise its connected subnet but suppresses neighbor Hello traffic. Removing the unintended passive setting enables the required adjacency exchange.
Incorrect Answers
A:Reference bandwidth affects cost calculation and will not enable Hello transmission on a passive OSPF interface.
C:A default route may affect user traffic reachability but does not undo passive-interface suppression of OSPF Hellos.
D:That would stop both peers from sending Hellos and make adjacency formation even less likely.
Question 471
On a broadcast Ethernet OSPF network, R1 is the DR and R2 is the BDR. R3 and R4 are DROTHER routers; their neighbor entry for each other remains 2WAY/DROTHER, but both are FULL with the DR and BDR. What should operations conclude?
- The R3–R4 two-way relationship is normally acceptable on a broadcast segment
- All OSPF neighbors must be FULL with every other neighbor, so restart both processes
- A mismatched area ID is proven solely by the 2WAY/DROTHER entry
- An OSPF passive interface can still exchange hellos normally with its peers
Explanation
Correct Answer
A:On broadcast networks, DROTHER peers often remain two-way with each other and synchronize fully with the DR and BDR.
Incorrect Answers
B:Full adjacency with all neighbors is typical of point-to-point links, but not a requirement between two DROTHER routers on a broadcast LAN.
C:The established two-way exchange and FULL adjacencies with DR and BDR do not establish an area-ID mismatch.
D:Passive-interface suppresses sending OSPF hellos; it cannot explain healthy FULL adjacencies already observed on the segment.
Question 472
On a dedicated Ethernet link between two OSPF routers, R1 is configured with point-to-point OSPF network type but R2 still uses broadcast mode. IP addressing and hello timers match. Which change targets the inconsistent adjacency behavior?
- Align both interfaces to a compatible OSPF network type for the actual link
- Force both routers to use identical local OSPF process ID numbers
- Replace the router ID with the same value on both ends of the link
- Set the same interface cost on both peers while leaving network types mismatched
Explanation
Correct Answer
A:OSPF network types affect expected neighbor and DR/BDR behavior; the peering interfaces should use mutually compatible settings for the link.
Incorrect Answers
B:A process ID is locally significant on Cisco IOS; two routers can peer using different process numbers when their actual OSPF parameters agree.
C:Duplicate router IDs produce identity conflicts and can prevent adjacency, so matching IDs would introduce an additional fault.
D:OSPF cost participates in shortest-path selection, not resolution of the inconsistent broadcast versus point-to-point network-type behavior.
Question 473
R1 sees a prefix in `show ip ospf database`, but `show ip route 10.99.0.0` selects an existing static route with administrative distance 1. Which statement best explains the absence of an OSPF-installed route?
- The OSPF LSA must be corrupt because no OSPF route appears in the forwarding table
- An OSPF-learned candidate can exist in the LSDB while the lower-AD static route wins RIB installation
- Every LSA always produces a separate route in the installed routing table
- The OSPF process must have shut down because the default route is static
Explanation
Correct Answer
B:OSPF calculates candidate routes from LSAs, but the RIB normally installs the lower-administrative-distance source for the same prefix.
Incorrect Answers
A:Having a route candidate in the link-state database is not itself evidence of corruption; competing route selection must be checked.
C:The link-state database represents topology information; route selection and policy can prevent an LSA-derived route from appearing in the RIB.
D:A static route can coexist with an active OSPF process; static preference alone does not indicate the process stopped.
Question 474
On Cisco IOS, a campus OSPFv2 process uses the default 100-Mb/s reference bandwidth. Its 1-Gb/s and 10-Gb/s Ethernet interfaces both receive automatic cost 1, preventing bandwidth differentiation. What process-level change fixes the scaling problem?
- Set ip ospf cost 1 manually on both interfaces to keep their metrics equal
- Set auto-cost reference-bandwidth 100000 under OSPF consistently on all routers in the domain
- Change the OSPF router ID to a higher numerical value on the 10-Gb/s side
- Increase both interfaces’ administrative distance without changing OSPF cost calculations
Explanation
Correct Answer
B:A higher common reference bandwidth lets OSPF calculate distinct metrics for 1-Gb/s versus 10-Gb/s links; use it consistently across the domain.
Incorrect Answers
A:Explicitly forcing cost 1 on both links reproduces rather than removes the unwanted tie between unlike bandwidths.
C:Router ID identifies the OSPF speaker for protocol exchanges; it is not the value used as cost-reference bandwidth.
D:Administrative distance influences selection between route sources, not the internal OSPF interface-cost computation described here.
Question 475
A technician can ping R2 from R1 across their connected subnet, but `show ip ospf neighbor` on R1 has no entry for R2. An ACL on the link permits ICMP but denies IP protocol 89. Which test or fix targets the missing OSPF neighbor?
- Permit OSPF IP protocol 89 across the intended peering interfaces and observe neighbor formation
- Change the DNS server of both routers because ICMP reachability was successful
- Allow only TCP port 89 instead of the IP protocol used by OSPF
- Force the OSPF routing cost to 1 so it can bypass an interface ACL
Explanation
Correct Answer
A:OSPF carries its own IP protocol number 89, not TCP/UDP port 89; allowing that protocol enables Hello and adjacency traffic.
Incorrect Answers
B:DNS name resolution is not needed to exchange OSPF protocol packets between neighboring IP interfaces.
C:TCP destination port 89 would not match OSPF packets, which have IP protocol 89 without a TCP header.
D:OSPF cost influences shortest-path calculation, but cannot override an ACL dropping control-plane OSPF packets.
Question 476
On a multiaccess OSPFv2 Ethernet segment, R3 is a participating neighbor but must never become DR or BDR, even after the current DR fails. Which interface election setting enforces this?
- Set OSPF priority to 255 on R3
- Use an OSPF reference bandwidth of zero
- Set its interface OSPF priority to 0
- Set its OSPF router ID to 0.0.0.0
Explanation
Correct Answer
C:An OSPF interface priority of zero explicitly disqualifies that router from DR and BDR election, although it may still form eligible neighbor adjacencies.
Incorrect Answers
A:The highest nonzero priority makes R3 a strong DR/BDR candidate, opposite to the no-candidacy requirement.
B:Reference bandwidth is related to cost calculation, not the DR election priority; zero is not a valid election control.
D:Router ID selection is a unique identifying function and is not a substitute for disabling DR eligibility with priority 0.
Question 477
On a new broadcast OSPF segment with no elected DR or BDR yet, the design intends Dist-A to be preferred over the other participating routers. Which election control should Dist-A have compared with the other eligible routers?
- The largest numeric interface OSPF cost
- Interface OSPF priority 0
- A lower router ID despite all other routers having higher OSPF priorities
- Give it the highest nonzero OSPF interface priority
Explanation
Correct Answer
D:The DR election compares nonzero OSPF interface priority first and router ID for equal priorities. A higher eligible priority prefers Dist-A in a new election.
Incorrect Answers
A:Interface cost chooses shortest paths; it does not rank DR or BDR candidates for broadcast-segment election.
B:Priority zero makes the router ineligible for DR/BDR and cannot give it preferential root status.
C:Router ID is a tie breaker after interface priority; a lower router ID cannot override a higher nonzero priority.
Question 478
Three OSPFv2 routers on an Ethernet broadcast segment all have interface priority 1 and no DR yet. The three elected router IDs are 1.1.1.1, 2.2.2.2 and 3.3.3.3. Which tie breaker identifies the most-preferred DR candidate?
- The router with the lowest IP interface address on the LAN
- Compare highest OSPF router ID
- The router whose interface has the lowest OSPF path cost
- The router that has the shortest hostname
Explanation
Correct Answer
B:With equal nonzero OSPF interface priorities during an election, the router with the highest elected OSPF router ID ranks highest; here 3.3.3.3 wins that tie breaker.
Incorrect Answers
A:IP interface numbering is not the direct DR tie breaker when OSPF priorities are equal; elected OSPF router ID matters.
C:Path cost affects route calculation, not the final DR-election tie break among equal-priority routers.
D:Device hostname length has no role in DR or BDR election.
Question 479
An OSPF broadcast network has an elected healthy DR. A new router joins with a higher interface priority than that DR, but no DR failure or new election occurs. What should the operator expect immediately?
- The new higher-priority router preempts the current DR instantly
- Account for nonpreemptive OSPF DR election
- Both routers become simultaneous DRs in the same broadcast segment
- OSPF floods the router priority through DNS to force reelection
Explanation
Correct Answer
B:OSPF DR/BDR election is nonpreemptive. A higher-priority newcomer does not automatically replace the existing DR unless election state changes appropriately.
Incorrect Answers
A:OSPF DR elections do not automatically preempt a stable incumbent solely because a higher-priority newcomer appears.
C:A single healthy broadcast network normally has one DR and one BDR; priority does not create two independent active DR roles.
D:DNS is unrelated to OSPF DR election and cannot cause the stated automatic takeover.
Question 480
An IOS operator needs to determine which OSPFv2 neighbors currently advertise FULL/DR, FULL/BDR or 2WAY/DROTHER on a shared broadcast subnet, and validate the local DR/BDR interface fields. Which displays should be inspected?
- Inspect show ip ospf neighbor and interface output
- show ip route static only
- show interfaces trunk and show vlan brief
- show ip nat translations and show arp
Explanation
Correct Answer
A:The neighbor display reports adjacency and DR/BDR roles while the interface display shows local OSPF network type, priority and elected designated routers.
Incorrect Answers
B:The static-route table does not show OSPF neighbor states, their router IDs or the local DR/BDR election result.
C:These are Layer 2 VLAN and trunk displays and cannot substitute for OSPF neighbor and interface election diagnostics.
D:NAT and ARP state have no OSPF neighbor adjacency roles or elected DR/BDR fields.
Cisco Certified Network Associate (CCNA) (200-301) Practice Tests
