Avaya Configuring IP Exterior Gateway Protocols (BGP and EGP) Manual de usuario descargar pdf (Pagina 32)

Configuring IP Exterior Gateway Protocols (BGP and EGP)

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308628-15.0 Rev 00

In addition, the BGP-4 update message can include the optional path attributes

listed in Table 1-3

BGP/OSPF Interaction

RFC 1745 defines the interaction between BGP and OSPF when OSPF is the IGP

within an autonomous system. For routers running both protocols, the OSPF

router ID and the BGP ID must be the same IP address. A BGP route policy must

be configured to allow BGP advertisement of OSPF routes.

Interaction between BGP-4 and OSPF includes the ability to advertise supernets

to support classless interdomain routing (CIDR). BGP-4 allows interdomain

supernet advertisements; OSPF can carry supernet advertisements within a

routing domain.

Table 1-3. BGP-4 Optional Path Attributes

Attribute Description

Multiexit discriminator Chooses between paths to the destinations listed

Local preference Allows AS border routers to indicate the preference

they assigned to a chosen route when advertising it

to IBGP peers

Atomic aggregate Ensures that certain network layer reachability

information (NLRI) is not deaggregated

Aggregator Identifies which AS performed the most recent route

aggregation. This attribute contains the last AS

number that formed the aggregate route followed by

the IP address of the BGP speaker that formed the

aggregate route.

Cluster list Lists the members of a route reflector cluster

Originator ID Identifies the originator of the route into a route

reflector cluster

BGP community Identifies the communities to which the route

belongs. (A community is a group of destinations that

share some common property.)

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Avaya Configuring IP Exterior Gateway Protocols (BGP and EGP) Manual de usuario Pagina 32