Avaya Configuring IP Exterior Gateway Protocols (BGP and EGP) Manual de usuario descargar pdf (Pagina 163)

Customizing EGP Services

308628-15.0 Rev 00

8-3

An EGP router does the following:

• Acquires EGP neighbors

• Determines neighbor reachability

• Exchanges network reachability information with its neighbors

Each of these capabilities has an associated phase in EGP: the neighbor

acquisition phase, the neighbor reachability phase, and the network reachability

phase, respectively.

In the acquisition phase, EGP is responsible for forming neighbor relationships

between routers that are peers. Routers that are peers each have an interface to a

common network. One router attempts to acquire a peer router. If the peer agrees

to be acquired, the two routers form a neighbor relationship. They then negotiate

the mode of operation and the polling modes.

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

modes. According to EGP, the routers’ modes are determined as shown in

Table 8-1

shows all possible acquisition mode combinations that are available

when you configure the EGP neighbors at each end of a connection. However,

Nortel Networks recommends that one router be configured in the active

acquisition mode and the other in the passive acquisition mode.

Table 8-1. Router Mode Determinator

Router A Router B Resulting Modes

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

Passive Passive Not allowed; at least one router must be active.

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 Exterior Gateway Protocols (BGP and EGP) Manual de usuario Pagina 163