Serial Link showing as OSPF Cost 1

[GRANT3779]

After posting - Just found that if I use the ospf cost command under the interface then the cost changes. Do I need to use both th interface ip ospf cost command AND amend the BW under the Interface? 

In my lab I have a P2P Serial link which is showing up as cost of 1 for OSPF. I would have expected this to show up as 1562? Am I missing something?

Bandwidth command under each interface is set to 64000.

I have configured the following and the relevant config on the other side of the link.

interface Serial0/1/0
bandwidth 64000
ip address 10.1.3.1 255.255.255.0
encapsulation ppp
no fair-queue
clock rate 64000
ppp authentication chap
end

R1_2801#sh ip ospf interface se0/1/0
Serial0/1/0 is up, line protocol is up
Internet Address 10.1.3.1/24, Area 0
Process ID 12, Router ID 1.1.1.1, Network Type POINT_TO_POINT, Cost: 1
Transmit Delay is 1 sec, State POINT_TO_POINT

[Rolf Fischer · Accepted solution]

Hi,

the Cisco OSPF implementation calculates the cost of an interface with the formula

cost = int [Reference-Bandwidth / Interface-Bandwidth].

The auto-cost reference-bandwidth is 100 Mbps by default and your interface-bandwidth is set to 64 Mbps (bandwidth command unit is kbps!); the result of the cost calculation is ~ 1,5 or 1 without the decimal positions.

The interface-level ip ospf cost command overwrites the auto-calculated value.

HTH
Rolf

[GRANT3779]

Hi Rolf, 

I have obviously not paid attention to the bandwidth command under the interface. It seems it is to be written in kbps rather than bps which is what i have seemed to have assumed!

Thanks again