Avaya Configuring IP Exterior Gateway Protocols (BGP and EGP) Uživatelský manuál stáhnout pdf (Strana 30)

Configuring IP Exterior Gateway Protocols (BGP and EGP)

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308628-14.00 Rev 00

BGP/OSPF Interaction

RFC 1403 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 identifier must be an IP address and must be identical. A

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.

BGP-4 Confederations

The BGP confederation feature can reduce the size and complexity of an IBGP

mesh by breaking large autonomous systems into a confederation of smaller

subautonomous systems. This division reduces the size of IBGP meshes and the

complexity of the associated configuration management. Other autonomous

systems view the confederation as a single autonomous system with the

confederation ID as its AS number. BGP confederations are available only with

BGP-4. The BGP-4 confederation feature complies with RFC 1965 and provides

the following functions:

Atomic aggregate Ensures that certain network layer reachability

information (NLRI) is not deaggregated

Aggregator Identifies which AS performed the most recent route

aggregation. The 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.

Route clusters Lists the route clusters that may be traversed to

reach a given destination

Advertiser Identifies which border router injected the route

BGP community Identifies the communities to which the route

belongs. (A community is a group of destinations that

share some common property.)

Table 1-2. BGP-4 Optional Path Attributes

(continued)

Attribute Description

1 2 ... 25 26 27 28 29 30 31 32 33 34 35 ... 307 308

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Avaya Configuring IP Exterior Gateway Protocols (BGP and EGP) Uživatelský manuál Strana 30