BGP Filtering: route-map or prefix-list

Unanswered Question
Jul 16th, 2008
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I'm curious about best practices regarding the usage of route-maps or prefix-list in the bgp config.


Some examples i've seen apply a prefix-list directly to a neighbor, others use a route-map.


I can't tell if there is a benefit one way or another.


Examples:

prefix-list applied to neighbor:

http://www.cymru.com/Documents/secure-bgp-template.html


prefix-list applied to route-map applied to neighbor:

router bgp 100

network 171.60.0.0

network 172.60.0.0

neighbor 200.69.232.70 remote-as 200

neighbor 200.69.232.70 route-map set-as-path out

!

route-map set-as-path 10 permit

match address 1

set as-path prepend 100 100

!

route-map set-as-path 20 permit

match address 2

!

access-list 1 permit 171.60.0.0 0.0.255.255

access-list 1 permit 172.60.0.0 0.0.255.255

!

access-list 2 permit 0.0.0.0 255.255.255.255

from http://www.cisco.com/en/US/docs/ios/12_2/ip/configuration/guide/1cfbgp.html#wp1040707


Thanks!


-Jeff

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milan.kulik Wed, 07/16/2008 - 12:06
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Hi,


IMHO, prefix-list just permits/denies prefixes while route-map can manipulate/change BGP attributes (local preference, MED, as prepend, etc.)


And to be precise, route-maps are matching as-path or ip access-lists, not prefix lists.


BR,

Milan

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