Redistribution static route into ospf (Metric-type 2)

Answered Question
Jul 6th, 2008
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Hi,


I try to redistribute static route 188.188.188.0/24 from Router 16A and 16B

with metric-type 2. I think 16C will have 2 equal cost route install in the routing table

E2 188.188.188.0 [110/20] 192.168.1.1

E2 188.188.188.0 [110/20] 172.20.1.9



However, after simulation, In noramal condition, router 16C has one route {E2 188.188.188.0 [110/20] 192.168.1.1}

installed. After 16C E0 down. 16C has one route {E2 E2 188.188.188.0 [110/20] via 172.20.1.9}

installed


Anyone know why Router 16C can't install 2x equal cost route ?

E2 188.188.188.0 [110/20] 192.168.1.1

E2 188.188.188.0 [110/20] 172.20.1.9



Correct Answer by n.nandrekar about 8 years 10 months ago

hi!

the router 16C will recieve both the routes with same metric but each of the routes will be advertised by different ASBR. So the route with the least distance to the ASBR will be the preffered route and thus only one is installed. Only when that goes down is the other one installed in the routing table.



Ref:

Section 16.4 paragraph (6.d) of the OSPF RFC.


"Type 2external paths advertising equal type 2 metrics are compared by looking at the distance to the forwarding addresses."


So this is as good as looking at both of them as E1 routes.. ;)

Regards,

Niranjan

(pls rate if helpful)

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Correct Answer
n.nandrekar Sun, 07/06/2008 - 07:18
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hi!

the router 16C will recieve both the routes with same metric but each of the routes will be advertised by different ASBR. So the route with the least distance to the ASBR will be the preffered route and thus only one is installed. Only when that goes down is the other one installed in the routing table.



Ref:

Section 16.4 paragraph (6.d) of the OSPF RFC.


"Type 2external paths advertising equal type 2 metrics are compared by looking at the distance to the forwarding addresses."


So this is as good as looking at both of them as E1 routes.. ;)

Regards,

Niranjan

(pls rate if helpful)

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