NSSA Area
Not-so-stubby-area. Similar to a stub area, except that a form of Type 1 and
Type 2 external routes can be learned from NSSAs. The external routes learned
from an NSSA are translated into corresponding external routes for the backbone
and other transit areas that accept external routes.
The NSSA is useful for areas that do not need to retain all the autonomous
system external route information flooded into the area, but do need to export
some limited external route information not permitted from standard OSPF stub
areas. As for stub areas, default costs can be set for NSSAs with the ComOS command
from the command line interface (PortMaster==>Command):
set ospf area Area stub-default-cost Number
External routes are not advertised into NSSAs.