Avaya Configuring IP Services Bedienungsanleitung PDF herunterladen (Seite 264)

Configuring IP Services

6-4

• Neighbor Acquisition Cease Message

When two routers have an established neighbor relationship, either of the

routers may send a Neighbor Acquisition Cease message to the other to end

the relationship. The status ﬁeld of the Neighbor Acquisition Cease message

header supplies the reason for ending the neighbor relationship.

• Neighbor Acquisition Cease Ack Response

This message is sent in response to a Neighbor Acquisition Cease message

and indicates that the peer received and accepts the message.

Modes

Once two routers agree to form a neighbor relationship, they must then negotiate

modes. Remember that in the Acquisition Request message, the requesting

neighbor supplies its acquisition mode, and in the Acquisition Conﬁrm Response

message the responding router supplies its acquisition mode. The acquisition

mode is conﬁgured for each router, and it can be active, passive, or both.

Ultimately, however, one of the routers must become the active router, and the

other router must become the passive router.

The router that becomes the active router will later be responsible for Hello

packets and Poll requests speciﬁed by the Hello Interval and the Poll Interval,

respectively. The passive router just responds to the active router with I-H-U and

Routing Update messages.

According to EGP, the routers’ modes are determined as shown in Table 6-1.

Table 6-1. Router Mode Determinator

Router A Router B Resulting Modes

Active Passive Router A is active; Router B is passive.

Passive Passive Not allowed.

Active Active The router with the lower autonomous system

number becomes active; the other becomes the

passive router.

Both Active Router A is passive; Router B is active.

Both Passive Router A is active; Router B is passive.

Both Both The router with the lower autonomous system

number becomes active; the other becomes the

passive router.

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Avaya Configuring IP Services Bedienungsanleitung Seite 264