OSPF is link-state routing protocol . It is most widely used Interior Gateway Protocol . It computes the shortest path route using a method based on Dijkstra’s algorithm . It allows routers to dynamically learn routes from one router and advertise that route to other routers . In this article we will discuss about some important Open Shortest Path First interview questions . If you are interviewing related to network administrator , this article is useful for you .
So Let’s start one by one Open Shortest Path First interview questions .
Open Shortest Path First Interview Questions
1. What is OSPF ?
OSPF stands for Open Shortest Path First . It is a link-state routing protocol. It is designed to support large network.
2. What is the Administrative Vlaue (AD) of OSPF ?
3. What are the characteristics of OSPF ?
The main characteristics of OSPF are –
- It support VLSM and CIDR
- It support unlimited hop count
- It support both IPv4 and IPv6
- It uses cost as its metric , which is computed based on bandwidth of link
4. What is router-id ?
It is a 32 bit unique identifier for each router.
5. What is LSA ?
LSA stands for Link State Advertisement . It hold topology information . It held in memory in the LSDB .
6. What is LSDB ?
LSDB stands for Link State Database . It stores LSA information .Each router has its own LSDB.
7. What is OSPF area ?
It is a logical collection of OSPF network , routers and link . OSPF network is divided into many smaller OSPF area , That’s why reducing the LSDB size .
8. What are the types of LSA in OSPF ?
types of LSA are –
- Router LSA
- Network LSA
- Summary LSA
- Summary ASBR LSA
- External LSA
- Multicast OSPF LSA
9. What are OSPF neighbor states ?
Down – send hello but not receive
Attempt – valid only for manually configuration neighbor
Init – receive hello from neighbor
2way – receive router id
Exstart – master/slave relationship stablished
Exchange – Check LSA in the database .
Loading – Actual exchange of OSPF information
Full – fully synchronized database
10. What is the configuration to change hello and dead interval ?
R# conf t
# in Se 0/0
# ip ospf hello-interval 10
# ip ospf dead-interval 40
11. What is Designated router and Backup Designated router ?
OSPF elect one router as a Designated router and one router as Backup designated router on the network . DR has highest priority in the network whereas BDR has second highest priority . The router has 0 priority dies not participate in DR/BDR selection .
Every router send LSA to DR through 220.127.116.11
DR send LSA to all router through 18.104.22.168
12. How to configure OSPF on your router ?
#router ospf 10
#network 10.0.0.0 0.255.255.255 area 0
#network 192.168.1.0 0.0.0.255 area 0
13. How to configure router-id on router ?
#router ospf 10
#router id 22.214.171.124
#clear ip ospf process
14. How to calculate OSPF cost ?
cost = Reference bandwidth/interface bandwidth
Reference bandwidth = 100 mbps
15. Explain tables maintain by OSPF ?
- Neighbor table – store information about OSPF neighbor
- Topology table – store topology structure of network
- Routing table – store best route to all know network
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In this article we discuss about Open Shortest Path First interview question . I hope this is useful for you.