OSPF Interview Questions


  • Why are loopbacks advertised as /32 host routes in OSPF?
  • Which command in OSPF shows the network LSA information?
  • What command would you use to create a totally stubby area?
  • What the Hello packet carries when we enable OSPF ?
  • What are LSA types?
  • What are area types? Why there are different area concepts?
  • What is the main importance of STUB network? Why it is been developed in OSPF?
  • What will happen if we redistribute between different process ?
  • What are the adjacency type? Is adjacency is formed in between all the OSPF enabled routers or not ?
  • What are EXSTART and EXCHANGE state?
  • If router ID are same between OSPF enabled routers will they form adjacency or not?
  • What is LSA 7 and how it can be used?
  • How we can connect a normal area to a backbone area if they are not directly connected?
  • What is LSA in case of OSPF? It resemblance to which properties of EIGRP?
  • What is OSPF’s metric? How is it identified in routing table? Does it support redistribution?
  • What are the states used in OSPF when forming neighbor ship?
  • What are the packet types does OSPF use? Explain Hello, Dead Timers, LSA, LSU, LSR packets.
  • What will be Hello/Dead timers in network having link capacity of >T1 and <=T1?
  • What is OSPF Router ID and how is it elected?
  • What is the DR/BDR in OSPF? How these are elected and in what scenario?
  • What are the multicast IPs used by OSPF? What multicast IP does DR/BDR router and non-DR use?
  • How do I change the reference bandwidth in OSPF?
  • How to generate default route in OSPF?
  • How external routes are advertised generally (E1 or E2)? How to change from E2 to E1?
  • What are the LSA’s available in STUB and totally stub network?
  • What is OSPF super Back Bone area?
  • What is the concept of auto-cost in OSPF?
  • IS there any DR and BDR concept in /31 network?
  • What are the different network types in OSPF?
  • How does OSPF calculate its metric or cost?
  • What algorithm is used by OSPF if equal cost routes exist?
  • Are OSPF routing protocol exchanges authenticated?
  • What is the link-state retransmit interval, and what is the command to set it?
  • What is the purpose of the variable IP-OSPF-Transmit-Delay?
  • Can an OSPF default be originated into the system based on external information on a router that does not itself have a default?
  • Can I use the distribute-list in/out command with OSPF to filter routes?
  • How can I give preference to OSPF interarea routes over intra-area routes?
  • Do I need to manually set up adjacencies for routers on the Switched Multimegabit Data Service (SMDS) cloud with the OSPF neighbor subcommand?
  • When routes are redistributed between OSPF processes, are all shortest path first algorithm (SPF) metrics preserved, or is the default metric value used?
  • How does Cisco accommodate OSPF routing on partial-mesh Frame Relay networks?
  • Which address-wild-mask pair should I use for assigning an unnumbered interface to an area?
  • Can I have one numbered side and leave the other side unnumbered in OSPF?
  • Why do I receive the "cannot allocate router id" error message when I configure Router OSPF One?
  • Why do I receive the "unknown routing protocol" error message when I configure Router OSPF One?
  • Is it true that only the static option of the virtual link in OSPF allows discontiguous networks, regardless of the mask propagation properties?
  • Are the multicast IP addresses mapped to MAC-level multicast addresses?
  • Does the Cisco OSPF implementation support IP TOS-based routing?
  • Does the offset-list subcommand work for OSPF?
  • Do I need any special commands to run OSPF over BRI/PRI links?
  • Which Cisco IOS Software release began support for per-interface authentication type in OSPF?
  • How can you detect the topological changes rapidly?
  • How does OSPF use two Multilink paths to transfer packets?
  • Can we have OSPF run over a GRE tunnel?
  • Is there a way to manipulate and prefer the Type 3 LSAs to originate from two different areas sent to the non-backbone area?
  • What is the maximum number of OSPF processes (VRF aware) on 7600/6500 platforms?
  • Is there a way to compare Cisco NX-OS/IOS OSPF commands?
  • Is there any feature of OSPF protocol for quick convergence and a slow reconvergence of routes?


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