Hi all,
When the metrics are same, RFC 3101 specifies the preference for NSSA/External
routes as follows.
In the section 2.5<https://tools.ietf.org/html/rfc3101#section-2.5> Calculating
Type-7 AS External Routes - 2.5.6.(e), it says..
(e) If the current LSA is functionally the same as an
installed LSA (i.e., same destination, cost and non-zero
forwarding address) then apply the following priorities in
deciding which LSA is preferred:
1. A Type-7 LSA with the P-bit set.
2. A Type-5 LSA.
3. The LSA with the higher router ID.
Points 1 and 2 are clear..
However Point 3 specifies preference of an LSA with a higher router ID. Why is
it so?
- Should we not install ECMP paths in this case?
- Is point 3 actually intended for NSSA translators to prefer a Type 7
LSA which needs to be used for translation to Type 5?
Considering the above 2 points, I guess point 3 needs to be modified in the RFC
to probably say..
3. Preference is same, install ECMP paths.
Additionally if the router is an NSSA translator, prefer
the LSA with higher router ID for Type 7-Type 5 translation.
Please let know any views/comments on the same.
Regards,
Balaji
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