OSPF Stub area question re: Default Routes

OSPF Stub area question re: Default Routes

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Subject Author Date
OSPF Stub area question re: Default Routes jimbo 06-17-2005
Posted by jimbo on June 17, 2005, 5:36 pm
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SETUP: When an OSPF area type is configured as STUB, then only a
default route will be advertised into the stub area by the Area Border
Router. No ASBRs or external routes will be advertised. FINE. But what
if there are two links connecting the stub area to area 0, meaning the
stub area has two ABRs. Furthermore, suppose one of those ABRs has a
shorter path to the ASBR (i.e. lower metric).

QUESTION: When each ABR advertises a default route into the stub area,
will the routers pick the default route with the lower metric? If not,
how will the stub areas routers choose from among the two candidate
default routes?

Thanx!
Jim



home networking made easy, greater protection, less stress, introducing nm 5.0, 728x90
Posted by John Agosta on June 18, 2005, 2:20 pm
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The internal routers will choose the default route pointing to the ABR with
the lowest cost,
from there, the ABR routes accordingly.


> SETUP: When an OSPF area type is configured as STUB, then only a
> default route will be advertised into the stub area by the Area Border
> Router. No ASBRs or external routes will be advertised. FINE. But what
> if there are two links connecting the stub area to area 0, meaning the
> stub area has two ABRs. Furthermore, suppose one of those ABRs has a
> shorter path to the ASBR (i.e. lower metric).
>
> QUESTION: When each ABR advertises a default route into the stub area,
> will the routers pick the default route with the lower metric? If not,
> how will the stub areas routers choose from among the two candidate
> default routes?
>
> Thanx!
> Jim
>




Posted by jimbo on June 19, 2005, 5:07 pm
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Understood. Thanx



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