OSPF employments “Cost” as the worth of the OSPF metric and utilizations a Reference Bandwidth of 100 Mbps for cost estimation. A cheaper demonstrates a preferable way over a greater expense. A directing convention utilizes a measurement to decide the best way of a bundle across an organization. An OSPF metric gives an indication of the upward across a specific connection point for bundle sending.
The expense of a connection point is conversely relative to the transfer speed of the point of interaction. Along these lines, a higher transmission capacity gives a lower cost and all the more upward and time defers equivalent a greater expense. In this manner, a 100-Mb/s Ethernet line has a greater expense than a 1000-Mb/s Ethernet line. The picture underneath shows the recipe for cost estimation
The worth of the reference cost is 100Mbps = 100,000,000 bps, So the recipe:
The default OSPF cost recipe doesn’t separate between communicates with data transmission quicker than 100 Mbps. The FastEthernet, Gigabit Ethernet, and 10 GigE interfaces share a similar expense on the grounds that the OSPF cost esteem should be a number. In this way, the default reference transfer speed is set to 100 Mb/s, and all interfaces that are quicker than Fast Ethernet likewise have an expense of 1. The expense an incentive for various sorts of connection points are the accompanying:
OSPF Accumulates Costs
The expense of an OSPF course is the amassed esteem from the source to the objective organization. For instance, in Figure 2, there are two courses from Router1 LAN to Router2 LAN. The expense to arrive at the Router2 LAN from Router1 LAN as follows:
First Route
Router1 Fast Ethernet 0/0 = 1
Router2 Ethernet = 10
The absolute expense to reach 192.168.20.0=11
second Route
Router1 Giga Ethernet 0/1 = 1
Router3 Serial 1/1/0 = 781
Router2 Ethernet = 10
All out cost to reach 192.168.20.0= 792
The steering table of Router1 for network 192.168.20.0 in Figure 3 affirms the OSPF metric to arrive at the Router2 LAN is an expense of 11.
Changing the Reference Bandwidth
OSPF involves 100 Mbps transfer speed for reference of any connections that are equivalent to or quicker than a quick Ethernet association. Along these lines, the expense relegated to a quick Ethernet with reference; transmission capacity of 100Mbps would equivalent to 1.
This computation works for quick Ethernet interfaces, So connects quicker than 100 Mb/s estimation isn’t simple in light of the fact that the OSPF metric just uses whole numbers as its last expense of a connection. In the event that the estimation is under a number, OSPF convention gathers together the worth to the nearest number.
Thus, according to the OSPF perspective, a point of interaction with a connection point transfer speed of 100 Mb/s, has a similar expense as a connection point with a data transmission of 1Gbps, 10Gbps and 100 Gbps. Along these lines, for making the best way assurance the reference; data transmission should be adjusted to a higher worth than 100Mbps to oblige quicker connects than 100Mbps.
Changing the Reference Bandwidth
Changing the reference data transmission doesn’t influence the real transfer speed limit on the connection. It essentially influences the OSPF metric estimation. We can change the reference; transfer speed with switch arrangement mode .
The arrangement should be same on each switch in the OSPF area. The worth is in Mbps, thus, to change the expenses for GigaEthernet the order would and for 10 Gigabit Ethernet .
To drop the default reference transmission capacity, utilize the order in switch design mode. The table in Figure-1 delineates the OSPF cost if the reference; transmission capacity is set to Gigabit Ethernet (1000) and the table in figure-2 outlines the OSPF cost if the reference; transfer speed is set to 10 Gigabit Ethernet joins. In table-1 the OSPF settle on better decisions since it can now separate among FastEthernet and Giga Ethernet joins. In Table-2 it is likewise separated between 100Mbps, 1G and 10G connections.
