It's sunday, got some time today. Let's wrap up this series quickly.
The physical and logical topology is gonna remain same. The only thing I changed in this part is ... IOS Version :)
R3 is Still the Translator:
Let's review the routing table of R2 quickly again and see how things are:
So now the question is why results are different with different IOS ? ( IOS used in part 1 was 12.4 (20) T ).
The previous version was actually following RFC 1587 in which the route preference is same as mentioned in post 1 i.e. E2 is preferred over N2.
But the later IOS followed the RFC3101 implementation. Which states that LSA with P-bit set is preferred over the one which has P bit as Zero. The P bit is set to 1 by ASBR while redistributing the routes into NSSA except the situation where ASBR is also ABR and P bit remains unset (0).
But as an Engineer if you would like you can still go back to older IOS behavior as following:
The reason in Part 1 , the traffic (Data Plane) took the direct path because of same cost to Forwarding Address.
Further Readings:
http://blog.ipspace.net/2008/01/e1-and-e2-routes-in-ospf.html
http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_ospf/configuration/15-e/iro-15-e-book/iro-ospfv2-nssa-cfg.html#GUID-C335FD95-ED21-4A51-894F-8B63119186EC
http://networklessons.com/ospf/ospf-path-selection-explained/#ixzz3GPsDJ8N8
HTH...
Deepak Arora
Evil CCIE
The physical and logical topology is gonna remain same. The only thing I changed in this part is ... IOS Version :)
R3 is Still the Translator:
Let's review the routing table of R2 quickly again and see how things are:
So now the question is why results are different with different IOS ? ( IOS used in part 1 was 12.4 (20) T ).
The previous version was actually following RFC 1587 in which the route preference is same as mentioned in post 1 i.e. E2 is preferred over N2.
But the later IOS followed the RFC3101 implementation. Which states that LSA with P-bit set is preferred over the one which has P bit as Zero. The P bit is set to 1 by ASBR while redistributing the routes into NSSA except the situation where ASBR is also ABR and P bit remains unset (0).
But as an Engineer if you would like you can still go back to older IOS behavior as following:
The reason in Part 1 , the traffic (Data Plane) took the direct path because of same cost to Forwarding Address.
Further Readings:
http://blog.ipspace.net/2008/01/e1-and-e2-routes-in-ospf.html
http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/iproute_ospf/configuration/15-e/iro-15-e-book/iro-ospfv2-nssa-cfg.html#GUID-C335FD95-ED21-4A51-894F-8B63119186EC
http://networklessons.com/ospf/ospf-path-selection-explained/#ixzz3GPsDJ8N8
HTH...
Deepak Arora
Evil CCIE
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