3com 3031 Instruccion De Instalación

C

HAPTER

 50: MBGP M

ULTICAST

 E

XTENSION

 C

ONFIGURATION

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Enable the router to report part or all of the SNPAs (Sub-network Points of 
Attachment, SNPA) saved in the local system.

The MP_UNREACH_NLRI is an optional non-transitive attribute that can be used 
for the purpose of withdrawing one or multiple unfeasible routes from service. It 
includes the following fields,

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AFI and SAFI.

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Withdrawn Routes: Contains one or multiple NLRIs, in which are the 
unreachable destination addresses.

An UPDATE packet that contains the MP_UNREACH_NLRI is not required to carry 
any other path attributes.

These two attributes enables MBGP to carry multi-protocol information. MSGP 
therefore supports both unicast and multicast by constructing different topology 
maps to implement appropriate policies. Besides, MBGP may construct different 
inter-domain routes for unicast and multicast under the same policy.

MBGP runs on a router in the following two modes:

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BGP (Internal BGP)

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EBGP (External BGP)

MBGP running in an autonomous system, is called IBGP; MBGP running across 
autonomous systemsis called EBGP.

MBGP offers four types of messages:

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Open Message

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Update Message

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Notification Message

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Keepalive Message

Open Message is the first message sent after the TCP connection is established. It 
is used to establish BGP peer relationship. Notification Message is used to notify 
errors. Keepalive message is used to check the validity of a connection. Update 
Message is the most important information in the MBGP system, used to 
exchange routing information among peers. It consists of three parts: the most: 
unreachable routes (MP_UNREACH_NLRI), Path Attributes, and Network 
Reachable Information (MP_REACH_NLRI).

Basic configuration tasks of MBGP multicast extension includes:

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Enable MBGP Multicast Extension Protocol

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Specify the network route to be advertised by MBGP multicast extension

Advanced configuration tasks of MBGP multicast extension includes:

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Configure the MED value for an AS

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Compare MED values from different AS neighbor paths

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Configure local preference

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Configure MBGP timers