Default information originate metric-type 1 / 2

[roger perkin]

I am looking for a good explanation on the behaviour of passing the metric when using default information originate in ospf

I have a customer with 2 internet connections the default route to ISP 2 has an ospf cost of 30000 on the outside interface which poisons the route

for the entire network so all traffic using ISP1

The requirement is to get the server to use ISP2 as it's default

I tried moving the ospf cost from int f0/1 onto f0/0

The default routing did not change, I then changed the default-information originate to metric-type 2

The default route changed so the server then used ISP2 as it's default route

Can anyone explain the difference between using metric-type 1 and metric-type 2

Diagram below

[smehrnia]

Hello Roger,

the difference between type 1 and type 2 is the way they are calculated:

Metric Type 1  includes both internal path costs + external cost.

Metric Type 2  is just the external cost, regardless of the internal network costs.

btw, if you have different paths to a same destination, the path with type 1 metric is always prefered.

here, your issue could have been from the different network path costs along the way which affected the final calculated cost, in case of type 1.

Hope it Helps,

Soroush.

[roger perkin]

Thank you for explaining that, I still have one issue. If I put ip  ospf cost 30000 on the interface on the right hand edge router which  joins area 0 from the router within area 0 the default route still goes  right?

My intention was to put a stop with the ip ospf cost 30000 forcing the core router to use the default route on the left

It seems to be ignoring my ospf cost?

Is this the correct way to achieve this goal?

Thanks in advance

Roger

[roger perkin]

If I put the cost on the other interface of the right Edge router which touches area 2 the core routes defualt left which is what I want.

I just need an explanation of why this happens?

Thanks

Roger

[smehrnia]

Hi,

from your Core router's point of view, there are two ways to get out to the internet, ISP1 and 2, and both are Inter-Area routes. when you increase the cost of the interface in its way to ISP2, it adds to the total metric calculated by the Core and if it makes greater cost than the one for ISP1 it makes that exit point least preferable.

if you want ur server to use ISP2 while the rest of the network ISP1, i'd suggest you do the manipulations on ur edge router.

Hope it helps and please rate helpful posts.

Soroush.

[cadet alain]

Hi,

OSPF will always use an intra-area route over an inter-area route even if the O route has a greater metric .

Regards.

Alain.

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