OSPF is a fancy protocol. To assist learners grasp summary its ideas, a unique strategy is taken -- Visualizing OSPF simulation. This tutorial, OSPF primary, simulates the fundamental OSPF actions on a easy topology: H1-R1-R2-H2. R1 and R2 are routers. H1 and H2 are hosts. This simulation reveals Four phases:
1) R1 and R2 aren't working OSPF. H1 ping H2. It fails.2) Start OSPF on two routers. R1 and R2 uncover one another as neighbors by flooding Hello.3) R1 and R2 develop Full relationship and synchronize their LSA (Link State Advertisement) database by sending DD, Request, and Update. R1 and R2 refresh their routing tables. H1 and H2 turn out to be reachable.4) H1 pings H2 once more. It succeeds this time.
Q1. What is OSPF?
Answer: OSPF is a hyperlink state routing protocol. OSPF routers change their Link State Advertisement (OSPF LSA) to study interface IP addresses from one another. Each router saves its LSAs in its Link State Database (LSDB.) Neighboring nodes synchronize their LSDBs. With constant LSDBs, OSPF routers are in a position to calculate shortest paths to achieve locations.
Q2. What does OSPF do?
Answer: Roughly, OSPF goes by way of the next phases:
1) OSPF node creates a Router LSA to explain its interface IP addresses. This LSA is probably the most primary LSA. 2) Routers uncover neighbors by flooding Hello. When a pair discover one another, they're in 2-way state. 3) Neighbors synchronize their LSDBs in three steps: i. Send DD to get LSDB catalog from one another. ii. Send Request to ask for lacking LSAs. iii. Send Update to transmit LSAs requested. When two neighbors have the identical LSDB, they're in Full Adjacency state. 4) With the identical LSDB, routers have constant information of the community topology and interface IP addresses. They can calculate routing paths independently and replace their routing tables. The assortment of routing tables from OSPF routers offers the shortest paths between locations.
Q3. What is Router LSA?
Answer: Each OSPF router creates a Router LSA to explain its interfaces' IP addresses. In a quite simple OSPF community, solely Router LSAs are wanted to calculate shortest paths.
This autumn. What does Router LSA do?
Answer: In a easy OSPF community (no LAN, no space), neighboring nodes change their Router LSAs and study what number of hyperlinks its neighbor has, and their interface IP addresses. After neighbor propagation, all OSPF nodes have the identical set of Router LSAs of their LSDBs. Now they've the identical information of community topology.
Q5. How can a router use LSDB to calculate routing paths?
Answer: From LSDB, an OSPF node learns the whole topology of the community: the variety of routers being related; Individual router's interfaces and their IP addresses; Interface hyperlink prices (OSPF metric). With such element data, OSPF calculates shortest paths to achieve all locations present in LSDB. For instance [a], within the OSPF simulation, R1's LSDB incorporates two Router LSAs:
1) R1 originated LSA incorporates two IP addresses: 192.168.1.0/24,192.168.3.0/30. 2) R2 originated LSA incorporates two IP addresses: 192.168.2.0/24,192.168.3.0/30. After LSDB synchronization, R1 and R2 each have these two LSAs. And they know that R1 and R2 are related by the hyperlink 192.168.3.0. Now R1 can calculate routing path to achieve distant vacation spot 192.11.68.2.2 and provides an entry (192.168.2.0/24, S1/0) to its routing desk.
Note [a]: This article is the FAQ of OSPF simulation. After studying, you possibly can play the interactive simulation listed in External Links. It visualize OSPF work move with shifting packets are altering tables.
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