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New Member

Which interface is added by OSPF cost?

Hi Sir,

I ask question of OSPF cost.

I want to know when add OSPF cost of interface.

When I configure 'ip ospf cost' on router's interface,

is OSPF cost added by incoming interface or outgoing interface?

Ryusuke.

1 ACCEPTED SOLUTION

Accepted Solutions

Re: Which interface is added by OSPF cost?

Hi Rick,

The OSPF cost is the outgoing cost for packets transmitted from this interface (used when executing the SPF tree by adding it to the cost of relevant path to the destination), do you mean with your statement that it is added to the cost of the incoming interface to calculate the whole path cost.

BR,

Mohammed Mahmoud.

5 REPLIES
Hall of Fame Super Silver

Re: Which interface is added by OSPF cost?

Ryusuke

The cost is added on the incoming interface.

HTH

Rick

New Member

Re: Which interface is added by OSPF cost?

Rick

Your answer is best.

Thank you.

Ryusuke

Re: Which interface is added by OSPF cost?

Hi Rick,

The OSPF cost is the outgoing cost for packets transmitted from this interface (used when executing the SPF tree by adding it to the cost of relevant path to the destination), do you mean with your statement that it is added to the cost of the incoming interface to calculate the whole path cost.

BR,

Mohammed Mahmoud.

Re: Which interface is added by OSPF cost?

Hi Ryusuke,

Why would you want to override the ospf cost on an interface? By default OSPF automatically calculates its matrics on interfaces participating in OSPF

based on the formula 100 Mbps devided by the interface total bandwidth.. a 64k link gets a metric of 1562, another example is a T1 1.544 gets a metric of 64 , 100 Megs link gets a metric of 1 and so on, the higher the bandwidth the lowest its cost and therefore prefered path and that matrics gets propagated through the OSPF domain . It is posible with the command you indicated to manipulate/override the default calculation on an interface, I have yet not seen a scenario where you would need to override the default behavior.

In the event you do need to change this

I would pay close attention which interfaces

participating in OSPF you need to change it,

remember that by chnaging the value to lower or higer it would inpact OSPF traffic desitions in chosing optimal path.

OSPF reference

http://www.cisco.com/en/US/tech/tk365/tk480/tsd_technology_support_sub-protocol_home.html

Q&A

http://www.cisco.com/en/US/tech/tk365/technologies_q_and_a_item09186a0080094704.shtml

HTH, please rate if this helps

Jorge

New Member

Re: Which interface is added by OSPF cost?

Hi Jorge

Thank you.

I configure it carefully.

This scenario is route control on same bandwidth interface.

Because,

there is different reliability network of same bandwidth in Japan.

My customer's policy don't use low reliability network for normal use.

Low reliability network is used for redundancy.(for backup route)

Ryusuke

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