Avaya Configuring IP, ARP, RARP, RIP, and OSPF Services Instrukcja Użytkownika Pobierz pdf (Strona 49)

IP Concepts, Terminology, and Features

308627-14.20 Rev 00

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The routing protocol announces routes to other routers in the network as follows:

The routing table manager forwards a route for advertisement to the protocol.

The protocol consults an announce policy to determine whether or not to

advertise the route to the network.

For instructions on configuring RIP policies, see “Configuring RIP Accept and

Announce Policies” on page 5-25.

For descriptions of IP import and export filter parameters, see Appendix B.

How OSPF Implements Routing Policies

OSPF applies accept and announce policies to routing information in several

different ways from the procedure shown in Figure 1-7. OSPF link state

advertisements (LSAs) are received and placed in the link state database (LSDB)

of the router. The information in the LSDB is also propagated to other routers in

the OSPF routing domain.

According to the OSPF standard, all routers in a given area must maintain a

synchronized database. To maintain database integrity across the network, a router

must not manipulate received LSAs before propagating them to other routers. To

accomplish this, OSPF accept and announce policies act in the following manner:

• OSPF accept policies control which OSPF non-self-originated external

routing information is passed to the routing table manager. The accept policies

control only what the local router uses; they do not affect the propagation of

external information, AS external routes, or type 7 LSAs to other routers.

• OSPF announce policies control which non-OSPF routes to advertise into the

OSPF domain. These routes are advertised in AS external routes or type 7

LSAs.

For instructions on configuring OSPF policies, see “Configuring OSPF Accept

and Announce Policies” on page 6-64.

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Avaya Configuring IP, ARP, RARP, RIP, and OSPF Services Instrukcja Użytkownika Strona 49