Avaya Configuring IP, ARP, RIP, and OSPF Services Bedienungsanleitung PDF herunterladen (Seite 36)

Configuring IP, ARP, RARP, RIP, and OSPF Services

1-14

308627-14.00 Rev 00

OSPF Addresses and Variable-Length Masks

A destination in an OSPF route advertisement is expressed as an IP address and a

variable-length mask. Together, the address and the mask indicate the range of

destinations to which the advertisement applies.

The ability to specify a range of networks allows OSPF to send one summary

advertisement that represents multiple destinations. For example, a summary

advertisement for the destination 128.185.0.0 with a mask of 0xffff0000 describes

a single route to destinations 128.185.0.0 through 128.185.255.255.

OSPF Neighbors

OSPF neighbors are any two routers that have an interface to the same network. In

each OSPF network, routers use the Hello protocol to discover their neighbors and

maintain neighbor relationships. On a broadcast or point-to-point network, the

Hello protocol dynamically discovers neighbors; however, on a nonbroadcast

multi-access network, you must manually configure neighbors.

The Hello protocol ensures that communication between neighbors is

bidirectional. Periodically, OSPF routers send out Hello packets over all

interfaces. Included in these Hello packets is the following information:

• The router’s priority

• The router’s Hello timer and dead timer values

• A list of routers that have sent Hello packets to this router on this interface

• The router’s choice for designated router and backup designated router

Bidirectional communication is verified when one router sees itself listed in the

neighbor’s Hello packet.

Neighbor Adjacencies

Neighbors may form an adjacency for the purpose of exchanging routing

information. When two routers form an adjacency, they go through a process

called database exchange to synchronize their topological databases. When their

databases are synchronized, the routers are said to be fully adjacent. From this

point on, only routing change information is passed between the routers, thus

conserving bandwidth.

1 2 ... 31 32 33 34 35 36 37 38 39 40 41 ... 373 374

Keine Kommentare

Avaya Configuring IP, ARP, RIP, and OSPF Services Bedienungsanleitung Seite 36