HCNP the principle and configuration of BGP protocol for learning Notes 3-route aggregation

The BGP protocol can use commands to aggregate specific routes into an aggregated route.

The route aggregation principle uses the longest same mask matching method.

Route aggregation can reduce the size of the routing table

No routing details can be used to reduce route flipping and not cause routing changes due to a single routing change

1 Auto-gather ( not available in the network, controllability is poor, can only be aggregated into the main type of network )

After the automatic aggregation is configured, the aggregated natural segment routes are generated, and the originally introduced subnets are suppressed and are not optimized and published to the BGP neighbors.

• Summary automatic //used to enable automatic aggregation of incoming routes

• Undo Summary Automatic //command used to cancel automatic aggregation of incoming routes

• By default, the incoming route is not automatically aggregated, that is, only the routes that are introduced are aggregated.

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2 Manual Aggregation

In general, manual aggregation takes precedence over the priority of auto-aggregation. By default, no route aggregation occurs.

By default, a manual aggregation will publish the detail and aggregation routes together.

aggregate ip-address Mask [ as-set | attribute-policy route-policy-name1 | detail-suppressed | origin-policy route -policy-name2 | Suppress-policy Route-policy-name3 ] //Manual aggregation, detail-suppressed (suppress detail)

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3 problems caused by route aggregation As-set

Issues to consider for BGP route aggregation

• Publishing of detail routes

• Inheritance of BGP routing properties

  • As-path

  • Origin

  • Community ...

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The As-path attribute of the aggregation route does not have any other as information, and the As-path information for all specific routes is lost.

It is stated that the aggregation route without the As_set parameter is considered to be generated by RTC.

Aggregate 160.0.0.0 255.0.0.0 detail-suppressed as-set //used to aggregate As-path information, add the aggregated As-path

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As_set information is important in avoiding routing loops because it records the as that is passed by the aggregated route.

4 Change route aggregation properties?? Attribute-policy

Aggregation routes do not inherit the original BGP route properties, and you can modify the aggregation route properties by command:

The configuration Attribute-policy parameter can be used to modify BGP aggregation route properties.

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5 filtering Routes Orgin-policy Suppress-policy

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• Origin-policy: Select a partial (meeting policy) Route aggregation

ACL number 2001

Rule deny source 1.1.3.0 0

Rule Permit Source any

Route-policy orgin Permit Node 20

If-match ACL 2001

aggregate 160.0.0.0 255.0.0.0 detail-suppressed As-set origin-policy Origin

Suppress-policy: Suppresses partial routing (suppresses all by default)

ACL number 2002

Rule Permit Source 1.1.1.0

Rule Permit Source 4.4.4.0

Route-policy Suppress Permit node 10

If-match ACL 2002

aggregate 160.0.0.0 255.0.0.0 detail-suppressed As-set origin-policy Origin suppress-policy suppress

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HCNP the principle and configuration of BGP protocol for learning Notes 3-route aggregation