Avaya Configuring Interface and Router Redundancy Manuel d'utilisateur télécharger pdf (Page 22)

Configuring Interface and Router Redundancy

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308626-14.00 Rev 00

Redundancy Protocol

Routers in a redundancy group all begin in the secondary role. A router assumes

the primary role according to the following criteria, which the redundancy

protocol considers in the following order:

Number of good interfaces

Number of reachable resources

Priority to become primary, which you configure (for more information, see

the Priority parameter in Chapter 5)

Lowest member ID (for more information, see the Member ID parameter in

Chapter 5)

For example, if two routers in a router redundancy group have the same number of

good interfaces, the protocol considers the number of reachable resources each

router has. But if one router has a larger number of good interfaces, that router

becomes primary without consideration of subsequent criteria.

The routers use a bidding process to determine which router becomes the primary

router. If the group has more than two members, the bidding process also

determines which of the backup routers is the best secondary router. The bidding

process consists of an exchange of messages called protocol data units (PDUs).

Table 2-1

provides a detailed description of this process.

Table 2-1. Redundancy Protocol PDU Flow Diagram for Role Bidding

Router A PDU Router B

Starts in secondary role. Starts in secondary role.

Sends Hello PDUs at periodic intervals.

These PDUs start the bidding for the

primary role.

Hello PDU

Role = Secondary

---------------->

Receives Hello PDU from Router A and

stores its contents in the redundancy group

database.

Checks to see if Router A is a better primary

router; if so, Router B does not plan to

change roles.

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Avaya Configuring Interface and Router Redundancy Manuel d'utilisateur Page 22