# ospf cost calculation

Feb 5th, 2007

Hi expert,

From the book , there is a default ospf metric all all different interface type ( e.g. Fast ethernet, ethernet ....), buti don't know how can this value can be obtained

Let 's say, the formula is cost = 10 to the power 8 / BW

if ethernet interface, then cost = 10 to the power 8 / 10 to the power 6, the result will be 10 to the power 2

So , how come the book answer of cost 10 come out ?

Hi

The formula for calculating OSPF cost is:-

10 to the power 8 / BW in bits/sec

So

Bandwidth calculation:

Ethernet = 10Mbits per sec = 10 x 1000 = 10000 kilobits x 1000 = 10000000 bits = 10 to the power 7

10 to the power 8 = 100000000

10 to the power 7 = 10000000

100000000 / 10000000 = 10

HTH

Jon

Overall Rating: 4.5 (2 ratings)

## Replies

Jon Marshall Mon, 02/05/2007 - 10:23

Hi

The formula for calculating OSPF cost is:-

10 to the power 8 / BW in bits/sec

So

Bandwidth calculation:

Ethernet = 10Mbits per sec = 10 x 1000 = 10000 kilobits x 1000 = 10000000 bits = 10 to the power 7

10 to the power 8 = 100000000

10 to the power 7 = 10000000

100000000 / 10000000 = 10

HTH

Jon