Understanding the network.pdf - Back to Home

The manner in which a route entry is created is indicated by the path
types. There are four OSPF path types:
• Intra-area paths—Paths to networks that are directly connected
to the router.
• Inter-area paths—Paths to networks that are in a different area,
but are within the boundaries of the OSPF domain.
• Type 1 external paths—Routes to destinations outside the OSPF
domain that have an OSPF cost associated with them.
• Type 2 external paths—Routes to destinations outside the OSPF
domain that have no OSPF cost. Type 2 is the default type used
for all external routes.
NOTE
When designing your network, keep in mind how path costs are
assigned, how they are used, and what kind of manipulation may be
needed to determine the best path.
OSPF's Value
Although the workings of OSPF are quite complex, the actual
configuration and operation are easy from an administrative point of
view. OSPF does require some pre-implementation planning, but its
speed and scalability make it an ideal choice for large enterprise
internetworks. The other element that makes OSPF attractive is that it
is an open standard and is widely implemented on most networking
hardware. This is important because no vendor has a perfect solution
for every problem.
TCP/IP Exterior Gateway Protocols
Exterior routing protocols (ERPs) are used primarily in Internet
backbone networks that connect internetworks. ERPs send
information the same way RIP does: as a vector (the AS number) and
as a distance (the destination network information). A simple way of
looking at ERPs is as a means for distributing static routes between
internetworks.