Top 90+ CCIE OSPF Interview Questions and Answers

by | Dec 9, 2022 | Free Resources

Here is a expert-curated list of frequently asked OSPF Questions and Answers

Are you preparing for an interview for a networking position that requires knowledge of OSPF? If so, you’ve come to the right place. In this blog post, we’ll provide a comprehensive list of frequently asked OSPF interview questions, along with detailed answers to help you ace your upcoming interview. Whether you’re a networking beginner or a seasoned pro, these questions and answers will provide valuable insights and help you feel confident and prepared for your interview. So let’s dive in and get started!

Question 1: What is OSPF?
Question 2: What Is Backbone Area?
Question 3: Why and on what environment do we implement OSPF?
Question 4: Why are loopbacks advertised as /32 host routes in OSPF?
Question 5: Mention some characteristics of OSPF?
Question 6: What is OSPF’s metric? How is it identified in routing table? Does it support redistribution?
Question 7: Explain LSA and its all Types such as LSA 1, 2, 3,4,5,7. When do we use LSA type 6?
Question 8: What is the concept of “auto cost reference-bandwidth” and in what scenarios we should use it?
Question 9: Why it’s known as Link state protocol? How it’s different than EIGRP? What algorithm does it use?
Question 10: Explain Area Border Router?
Question 11: What will happen if we make priority of an OSPF router as “zero”?
Question 12: How do I change the reference bandwidth in OSPF?
Question 13: How does OSPF calculate its’ metric or cost?
Question 14: How Do We Configure OSPF Routing Protocol?
Question 15: What are Different OSPF LSA Types?
Question 16: What are the states used in OSPF when forming neighborship?
Question 17: What Is Autonomous System Border Router?
Question 18: What are different neighbor states in OSPF?
Question 19: Which type of area blocks external route?
Question 20: What algorithm is used by OSPF if equal cost routes exist?
Question 21: What are the multicast IPs used by OSPF? What multicast IP does DR/BDR router and non-DR use?
Question 22: What are the packet types does OSPF use? Explain Hello, Dead Timers, LSA, LSU, LSR packets.
Question 23: What is role of topology and routing table in OSPF?
Question 24: What Is OSPF Router-Id?
Question 25: Does DR/BDR election happen in OSPF Point to Point Network?
Question 26: What are the tables Maintained By OSPF?
Question 27: What is the link-state retransmit interval, and what is the command to set it?
Question 28: What different activities neighbour router perform in OSPF?
Question 29: What is the purpose of the variable IP-OSPF-Transmit-Delay?
Question 30: Is it true that only the static option of the virtual link in OSPF allows discontiguous networks, regardless of the mask propagation properties?
Question 31: On which algorithms OSPF depends? What is the principle behind it?
Question 32: Are the multicast IP addresses mapped to MAC-level multicast addresses?
Question 33: Does the Cisco OSPF implementation support IP TOS-based routing?
Question 34: What is the concept of Virtual-link in OSPF? Can virtual link be formed thru stub area?
Question 35: Does the offset-list subcommand work for OSPF?
Question 36: Can an OSPF default be originated into the system based on external information on a router that does not itself have a default?
Question 37: Briefly explain functioning and working of different OSPF?
Question 38: Can I use the distribute-list in/out command with OSPF to filter routes?
Question 39: How can I give preference to OSPF interarea routes over intra-area routes?
Question 40: What Is The Default Dead Interval?
Question 41: What LSA is used for inter area communication? What LSA type is used for inter protocol communication in OSPF?
Question 42: What are the different OSPF network types and give an example for each?
Question 43: Do I need to manually set up adjacencies for routers on the Switched Multimegabit Data Service (SMDS) cloud with the OSPF neighbor subcommand?
Question 44: Explain the concept of Area Border Router (ABR) and Autonomous System Border Router (ASBR). Can router sitting between area 2 and 3 be called as ABR?
Question 45: How OSPF inter area, external routes are denoted or represented in routing table?
Question 46: When routes are redistributed between OSPF processes, are all shortest path first algorithm (SPF) metrics preserved, or is the default metric value used?
Question 47: Name tables which OSPF maintain? Question 48: What is the DR/BDR in OSPF? How these are elected and in what scenario?
Question 49: How does Cisco accommodate OSPF routing on partial-mesh Frame Relay networks?
Question 50: Which address-wild-mask pair should I use for assigning an unnumbered interface to an area?
Question 51: What Is The Need For Dividing The Autonomous System Into Various Areas?
Question 52: Can I have one numbered side and leave the other side unnumbered in OSPF?
Question 53: Why do I receive the “cannot allocate router id” error message when I configure Router OSPF One?

Question 54: What Is The Benefit Of Dividing The Entire Network Into Areas?
Question 55: Why do I receive the “unknown routing protocol” error message when I configure Router OSPF One?
Question 56: What Is The Default Hello Interval?
Question 57: What do the states DR, BDR, and DROTHER mean in show ip OSPF interface command output?
Question 58: When I issue the show ip OSPF neighbor command, why do I only see FULL/DR and FULL/BDR, with all other neighbors showing 2-WAY/DROTHER?
Question 59: Why do I not see OSPF neighbors as FULL/DR or FULL/BDR on my serial link?
Question 60: Do I need any special commands to run OSPF over BRI/PRI links?
Question 61: Explain OSPF Timers?
Question 62: Do I need any special commands to run OSPF over asynchronous links?
Question 63: Which Cisco IOS Software release began support for per-interface authentication type in OSPF?
Question 64: Can I control the P-bit when importing external routes into a not-so-stubby area (NSSA)?
Question 65: Why are OSPF show commands responding so slowly?
Question 66: What does the clear ip OSPF redistribution command do?
Question 67: Does OSPF form adjacencies with neighbors that are not on the same subnet?
Question 68: What Are The Steps Required To Change Neighborship Into Adjacency?
Question 69: How often does OSPF send out link-state advertisements (LSAs)?
Question 70: How do I stop individual interfaces from developing adjacencies in an OSPF network?
Question 71: When I have two type 5 link-state advertisements (LSAs) for the same external network in the OSPF database, which path should be installed in the IP routing table?
Question 72: Explain OSPF LSA, LSU And LSR?
Question 73: What problems can cause OSPF neighborship in “down” state?
Question 74: Where does the summarization happen in OSPF? Which command is used for summarization at ABR and at ASBR?
Question 75: Should I use the same process number while configuring OSPF on multiple routers within the same network?
Question 76: I have a router that runs Cisco Express Forwarding (CEF) and OSPF, who does load-balancing when there are multiple links to a destination?
Question 77: What is “Process-id”? Does it have local or global significance? Does it need to be same on OSPF neighbor routers?
Question 78: How does OSPF use two Multilink paths to transfer packets?
Question 79: How can you detect the topological changes rapidly?
Question 80: Explain The Various OSPF States?
Question 81: Can we have OSPF run over a GRE tunnel?
Question 82: Is there a way to manipulate and prefer the Type 3 LSAs to originate from two different areas sent to the non-backbone area?
Question 83: Is there a drop/flap of an OSPF neighborship when changing an OSPF area type from NSSA no-summary to NSSA?
Question 84: Why DR And BDR Are Elected In OSPF?
Question 85: What is the concept of “Area” in OSPF? What is Backbone area, stub area, Totally Stubby Area, Not So Stubby area (NSSA)?
Question 86: In the %OSPF-5-ADJCHG: Process ID, Nbr [ip-address] on Port-channel31 from FULL to EXSTART, SeqNumberMismatch error message, what does SeqNumberMismatch signify?
Question 87: How does ISPF impact or improve the OSPF network?
Question 88: Is there a way to compare Cisco NX-OS/IOS OSPF commands?
Question 89: Is there any feature of OSPF protocol for quick convergence and a slow re-convergence of routes?
Question 90: What does BADSEQNUM in the %OSPF-5-NBRSTATE: OSPF-101 [5330] Process 101, Nbr on Vlan7 02 from FULL to EXSTART, BADSEQNUM OSPF log message mean?
Question 91: What will be Hello/Dead timers in network having link capacity of >T1 and <=T1?
Question 92: What Parameters Must Match For Two Routers To Become Neighbors?
Question 93: What is O E1, O E2 letters in OSPF? Which is default external type 1 or external type 2?


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