What metric does OSPF use to find the best routes?
OSPF uses a cost metric that represents the status of the link and the bandwidth of the interface in an algorithm to determine the best route to a destination. The algorithm used is called the SPF (shortest path first) or Dijkstra algorithm.
What algorithm does OSPF use to calculate metric?
OSPF uses SPT tree to calculate the best route for routing table. A SPT tree cannot grow beyond the area. So if a router has interfaces in multiple areas, it needs to build separate tree for each area. SPF algorithm calculates all possible routes from source router to destination network.
How do I change metric value in OSPF?
Cisco routers have three methods to change the OSPF interface cost:
- By directly using the interface command ‘ip ospf cost <1-65535>’ Router#conf t Router(config)#int gi0/0/0 Router(config-if)#ip ospf cost <1-65535>
- Changing the ‘interface bandwidth’ setting (in kilobits), which changes the calculated value.
Why we use OSPF?
The main advantage of a link state routing protocol like OSPF is that the complete knowledge of topology allows routers to calculate routes that satisfy particular criteria. This can be useful for traffic engineering purposes, where routes can be constrained to meet particular quality of service requirements.
How does OSPF use the cost metric?
Open Shortest Path First (OSPF) uses “Cost” as the value of metric and uses a Reference Bandwidth of 100 Mbps for cost calculation. The formula to calculate the cost is Reference Bandwidth divided by interface bandwidth. For example, in the case of 10 Mbps Ethernet , OSPF Metric Cost value is 100 Mbps / 10 Mbps = 10.
Which algorithm is used by OSPF?
shortest path first (SPF) algorithm
OSPF uses the shortest path first (SPF) algorithm to determine routes that should be added to the routing table. OSPF routers maintain a map of the internetwork called the link state database.
How does OSPF calculate its metric or cost?
Why OSPF is called Link-State?
The OSPF protocol is a link-state routing protocol, which means that the routers exchange topology information with their nearest neighbors. The topology information is flooded throughout the AS, so that every router within the AS has a complete picture of the topology of the AS.
Which layer is OSPF?
OSPF and BGP belong to the Application Layer.
Where is OSPF used?
OSPF (Open Shortest Path First) is an Interior Gateway Protocol (IGP). It’s used to decision routing in the autonomous systems. It realizes the Link State Routing Protocol, belonging to IGP, so that it works in the internal system.