Not-so-stubby-areas (NSSAs) are similar to the existing OSPF (Open Shortest Path First) stub area configuration option but have the following two additional capabilities:
External routes originating from an ASBR connected to the NSSA can be advertised within the NSSA.
External routes originating from the NSSA can be propagated to other areas, including the backbone area.
The CLI command to control the NSSA function is similar to the command used for configuring a stub area, as follows:
configure ospf area area-identifier nssa [summary | nosummary] stub-default-cost cost {translate}
The translate option determines whether type 7 LSAs are translated into type 5 LSAs. When configuring an OSPF area as an NSSA, translate should only be used on NSSA border routers, where translation is to be enforced. If translate is not used on any NSSA border router in a NSSA, one of the ABRs for that NSSA is elected to perform translation (as indicated in the NSSA specification). The option should not be used on NSSA internal routers. Doing so inhibits correct operation of the election algorithm.
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