Installing and Administering Internet Services

Chapter 8 343
Configuring gated
Configuring the OSPF Protocol
1. If your AS will be exchanging routing information with other
autonomous systems, you need to obtain a unique AS number from
the Internet Assigned Numbers Authority.
2. Partition the AS into areas. Any inter-connected networks can be
partitioned into lists of address ranges, with each address range
represented as an address-mask pair. The area border routers will
summarize the area contents for each address range and distribute
the summaries to the backbone. For more information on specifying
address ranges, see “Networks” on page 345.
3. Identify the internal routers for each area. An internal router
configuration will contain only one area definition.
4. Identify the area border routers and the areas to which they
interface. The configuration for each area border router will contain
multiple area definitions.
5. For each router, determine the types of interface to each area. Router
interfaces can be multicast, non-broadcast multi-access (NBMA), or
point-to-point. For more information on router interfaces, see
“Interfaces” on page 346.
6. For multi-access networks, identify a Designated Router. For NBMA
networks, several routers can be Designated Router candidates.
Designated Routers are specified in the interface definitions (see
“Interfaces” on page 346).
7. Decide if you want to assign a cost to each interface. For more
information about costs, see “Cost” on page 359.
8. Designate stub areas. AS external link advertisements are
propagated to every router in every area in an AS, except for routers
in configured stub areas. For more information, see “Stub Areas” on
page 353.
9. Identify backbone routers. The router configuration will contain a
backbone definition and a virtual link definition, if necessary. For
more information, see “Defining Backbones” on page 355.
10.Determine if routing packets will be authenticated for each area. For
more information, see “Authentication” on page 357.
11.IdentifyAS boundary routers. For more information, see “AS External
Routes (AS Boundary Routers Only)” on page 360.