Brocade FastIron Ethernet Switch Layer 3 Routing Configura Instrukcja Użytkownika Pobierz pdf (Strona 437)

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Filtering

This section describes the following:

• AS-path filtering

• Route-map continue clauses for BGP4 routes

• Defining and applying IP prefix lists

• Defining neighbor distribute lists

• Defining route maps

• Router-map continue clauses for BGP4 routes

• Configuring cooperative BGP4 route filtering

AS-path filtering

You can filter updates received from BGP4 neighbors based on the contents of the AS-path list

accompanying the updates. For example, to deny routes that have the AS 10.3.2.1 in the AS-path from

entering the BGP4 route table, you can define a filter.

The device provides the following methods for filtering on AS-path information:

• AS-path filters

• AS-path ACLs

NOTE

The device cannot support AS-path filters and AS-path ACLs at the same time. Use one method or the

other, but do not mix methods.

NOTE

Once you define a filter or ACL, the default action for updates that do not match a filter is deny . To

change the default action to permit , configure the last filter or ACL as permit any any .

AS-path filters or AS-path ACLs can be referred to by the filter list number of a BGP4 neighbor as well

as by match clauses in a route map.

Defining an AS-path ACL

To configure an AS-path list that uses "acl 1", enter a command such as the following.

device(config)# ip as-path access-list acl1 permit 100

device(config)# router /jointfilesconvert/1441084/bgp

device(config-/jointfilesconvert/1441084/bgp-router)# neighbor 10.10.10.1 filter-list acl1 in

Syntax: [no] ip as-path access-list string [ seq s eq-value ] deny | permit regular-expression

The ip as-path command configures an AS-path ACL that permits routes containing AS number 100 in

their AS paths. The neighbor command then applies the AS-path ACL to advertisements and updates

received from neighbor 10.10.10.1. In this example, the only routes the device permits from neighbor

10.10.10.1 are those whose AS-paths contain AS-path number 100.

The string parameter specifies the ACL name. (If you enter a number, the CLI interprets the number as

a text string.)

The seqseq-value parameter is optional and specifies the sequence number for the AS-path list. If you

do not specify a sequence number, the software numbers in increments of 5, beginning with number 5.

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