Dell Force10 E300, Configuration Manual, Page: 694 / 1262

694 | Open Shortest Path First (OSPFv2 and OSPFv3)
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A Stub Area (SA) does not receive external route information, except for the default route. These areas do
receive information from inter-area (IA) routes. Note that all routers within an assigned Stub area must be
configured as stubby, and no generate LSAs that do not apply. For example, a Type 5 LSA is intended for
external areas and the Stubby area routers may not generate external LSAs. Stubby areas cannot be
traversed by a virtual link.
A Not-So-Stubby Area (NSSA) can import AS external route information and send it to the Backbone. It
cannot received external AS information from the Backbone or other areas. It can be traversed by a virtual
link.
Totally Stubby Areas are referred to as No Summary areas in FTOS.
Networks and Neighbors
As a link-state protocol, OSPF sends routing information to other OSPF routers concerning the state of the
links between them. The state (up or down) of those links is important.
Routers that share a link become neighbors on that segment. OSPF uses the hello protocol as a neighbor
discovery and keep alive mechanism. After two routers are neighbors, they may proceed to exchange and
synchronize their databases, which creates an adjacency.
Router Types
Router types are attributes of the OSPF process. A given physical router may be a part of one or more
OSPF processes. For example, a router connected to more than one area, receiving routing from a BGP
process connected to another AS acts as both an Area Border Router and an Autonomous System Router.
Each router has a unique ID, written in decimal format (A.B.C.D). The router ID does not have to be
associated with a valid IP address. However, Force 10 recommends that the router ID and the router’s IP
address reflect each other, to make troubleshooting easier.
Figure 32-2 gives some examples of the different router designations.
Note: You can log adjacency state changes for OSPFv2 and v3 with the command
log-adjacency-changes
from ROUTER OSPF mode.