Refer to the Exhibit.
Referring to the OSPF link metrics in the exhibit, which path will traffic from R6 take to reach R1?
A.
R6, R3, R2, R4, R1
B.
R6, R3, R2, R1
C.
R6, R5, R4, R1
D.
R6, R5, R3, R2, R4, R1
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A = 5+5+5+5 = 20
B = 5+5+20 = 30
Correct is A?
Another example:
http://www.aiotestking.com/juniper/2012/11/in-the-exhibit-which-cost-does-r5-calculate-to-reach-the-172301024-network
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B is correct since intra-area is preferred over inter-area on R2 in this case
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you are right
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Sf and Mostager. Please explain your logic
if intra-area routes are prefered over inter-area routes, then R2 will prefer the intra-area route from R4 as opposed to R1. Even considering the metrics from R2 to R4 to R1 is 10 (5+5) compared to metric directly from R2 to Ra (20)
So using both logics, I believe answer A is correct.
unless someone can explain otherwise
Thanks
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B is the correct answer
Please see RFC 2328 below and how it defines intra-area path.
RFC 2328 section 11
http://www.ietf.org/rfc/rfc2328.txt
Path-type
There are four possible types of paths used to route traffic to
the destination, listed here in decreasing order of preference:
intra-area, inter-area, type 1 external or type 2 external.
Intra-area paths indicate destinations belonging to one of the
router’s attached areas. Inter-area paths are paths to
destinations in other OSPF areas. These are discovered through
the examination of received summary-LSAs. AS external paths are
paths to destinations external to the AS. These are detected
through the examination of received AS-external-LSAs.
also see explanation in this link
https://supportforums.cisco.com/thread/2239499
If intra area paths are destinations belonging to one of the routers attached areas, then since R2 is attached to area 0 and area 1, then the path from R2 to R1 is an intra-area path. And the route from R1 advertised through R4 is coming in as LSA 3 (summary LSA) hence becomes an inter-area path.
This is how answer B becomes correct.
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