Redistribution static, connected route into ospf

[acbenny]

Hi all,

Attach is the config and diagram for your reference. I can success to redistribute static route (188.188.188.0/24) and connected route (10.10.11.0/24). into ospf domain.

From my understanding. Metric-type 1 will calculate the sum of internal cost and external cost(default cost 20).

According to the outcome of routing table of 16A router, There are two routes I don't understand

E1 188.188.188.0 [110/40]

E1 10.10.11.0/24 [110/30]

From my understanding, I expect outcome will be as below

E1 188.188.188.0 [110/30]

E1 10.10.11.0/24 [110/30]

because a default cost 20 for ALL static and connected route will be generated into ospf

domain. In addition to the Internal cost that ethernet media between 36 router and 16A router which

cost is 10. So my expect outcome will be

E1 188.188.188.0 [110/30]

E1 10.10.11.0/24 [110/30]

Any expert can tell me why. Thank you for your help

[ralphcarter]

Hmm, this has me puzzled also. I'm looking at my production routers setup in a similiar way and I'm getting (type 5 LSA = 20) + route metric, which would be similiar to your 30 and not 40.

[ralphcarter]

Ahh wait, its because your both advertising the 1.1.1.0 network to OSPF and redistibuting it at the same time.

So if you look at Router 16A, it has a route:

O 1.1.1.0 [110/20] via 10.1.1.1, 00:28:14, Ethernet1

This 20 + the redistributed metric = 40.

To fix this, dont redistribute connected networks when you advertise them already with the network command.

[acbenny]

Sorry ralphcarter ,

the 1.1.1.0/24 is considered as O route. I think it is ok.

I just don't understand why metric value of 188.188.188.0 is 40, why not 30 ?

E1 188.188.188.0 [110/40]

[ralphcarter]

What happens if you do this on Router 36.

Remove: redistribute connected metric-type 1 subnets

Add: network 10.10.11.1 0.0.0.0 area 0

Can you try this and see if it changes the metric?

[a.alekseev]

what is the ospf cost for link 1.1.1.0/24 on 36?

[acbenny]

Hi,

the network 1.1.1.0/24 is located at fastEthernet 0/0 in 36.

36 Routing table show below.

1.0.0.0/24 is subnetted, 1 subnets

C 1.1.1.0 is directly connected, FastEthernet 0/0

[Nagendra Kumar Nainar · Accepted solution]

Benny,

When you configure a static route with next hop which is also configured as part of OSPF, it will consider the ospf cost of tht interface as well.

So in your case, you have configured

"ip route 188.188.188.0 255.255.255.0 1.1.1.2" where 1.1.1.0 network is also a part of OSPF domain.

Now when the metric is calculated, it will include default_cost+cost_to_reach_Static_NH+cost_to_reach_ASBR (20+10+10) so you get 40 as metric. Try removing 1.1.1.0 network from OSPF doamin and see if it changes.

HTH,

Nagendra_

[acbenny]

Thank your very much !