Hello,
Je suis en train de réfléchir sur la bonne méthode pour l'utilisation filtrage AS-PATH lorsqu’il y a 3 transits.
2 transits seront utilisés en priorité, le 3ème en backup car plus cher sur la bande passante
local-preference 200 => AS6939
local-preference 200 => AS174
local-preference 100 => AS2914
J’ai dans l’idée de vouloir privilégier les réseaux directement connectés aux AS de transit = chemin plus court, est-ce que cela est une bonne méthode ??
Comment gérer le cas ou 2 transits voire les 3 sont directement connectés au même réseau de destination ??
Par exemple X.X.X.X est directement connecté sur 6939/174/2914, vers quel transit BGP va-t-il envoyer le flux ??
J’ai commencé à écrire la conf suivante :
!
router bgp XYZ
neighbor 1.1.1.1 remote-as 6939
neighbor 1.1.1.1 route-map filter-on-as-path in
neighbor 1.1.1.1 filter-list 1 out
neighbor 2.2.2.2 remote-as 2914
neighbor 2.2.2.2 route-map filter-on-as-path in
neighbor 2.2.2.2 filter-list 1 out
neighbor 3.3.3.3 remote-as 174
neighbor 3.3.3.3 route-map filter-on-as-path in
neighbor 3.3.3.3 filter-list 1 out
!
route-map filter-on-as-path permit 10
match as-path 100
set local-preference 80
!
route-map filter-on-as-path permit 20
match as-path 101
set local-preference 80
!
route-map filter-on-as-path permit 30
match as-path 102
set local-preference 200
!
route-map filter-on-as-path permit 40
match as-path 110
set local-preference 80
!
route-map filter-on-as-path permit 50
match as-path 111
set local-preference 80
!
route-map filter-on-as-path permit 60
match as-path 112
set local-preference 100
!
route-map filter-on-as-path permit 70
match as-path 120
set local-preference 80
!
route-map filter-on-as-path permit 80
match as-path 121
set local-preference 80
!
route-map filter-on-as-path permit 90
match as-path 122
set local-preference 200
!
ip as-path access-list 1 permit ^$
ip as-path access-list 100 permit ^6939_174_
ip as-path access-list 101 permit ^6939_2914_
ip as-path access-list 102 permit ^6939_[0-9]*$
ip as-path access-list 110 permit ^2914_174_
ip as-path access-list 111 permit ^2914_6939_
ip as-path access-list 112 permit ^2914_[0-9]*$
ip as-path access-list 120 permit ^174_2914_
ip as-path access-list 121 permit ^174_6939_
ip as-path access-list 122 permit ^174_[0-9]*$
router bgp XYZ
neighbor 1.1.1.1 remote-as 6939
neighbor 1.1.1.1 route-map filter-on-as-path in
neighbor 1.1.1.1 filter-list 1 out
neighbor 2.2.2.2 remote-as 2914
neighbor 2.2.2.2 route-map filter-on-as-path in
neighbor 2.2.2.2 filter-list 1 out
neighbor 3.3.3.3 remote-as 174
neighbor 3.3.3.3 route-map filter-on-as-path in
neighbor 3.3.3.3 filter-list 1 out
!
route-map filter-on-as-path permit 10
match as-path 100
set local-preference 80
!
route-map filter-on-as-path permit 20
match as-path 101
set local-preference 80
!
route-map filter-on-as-path permit 30
match as-path 102
set local-preference 200
!
route-map filter-on-as-path permit 40
match as-path 110
set local-preference 80
!
route-map filter-on-as-path permit 50
match as-path 111
set local-preference 80
!
route-map filter-on-as-path permit 60
match as-path 112
set local-preference 100
!
route-map filter-on-as-path permit 70
match as-path 120
set local-preference 80
!
route-map filter-on-as-path permit 80
match as-path 121
set local-preference 80
!
route-map filter-on-as-path permit 90
match as-path 122
set local-preference 200
!
ip as-path access-list 1 permit ^$
ip as-path access-list 100 permit ^6939_174_
ip as-path access-list 101 permit ^6939_2914_
ip as-path access-list 102 permit ^6939_[0-9]*$
ip as-path access-list 110 permit ^2914_174_
ip as-path access-list 111 permit ^2914_6939_
ip as-path access-list 112 permit ^2914_[0-9]*$
ip as-path access-list 120 permit ^174_2914_
ip as-path access-list 121 permit ^174_6939_
ip as-path access-list 122 permit ^174_[0-9]*$
