Configuring External BGP
Router A in AS100
interface ethernet 5/0
ip address 222.222.10.2 255.255.255.240
router bgp 100
network 220.220.8.0 mask 255.255.252.0
neighbor 222.222.10.1 remote-as 101
neighbor 222.222.10.1 prefix-list RouterC in
neighbor 222.222.10.1 prefix-list RouterC out
Router C in AS101
interface ethernet 1/0/0
ip address 222.222.10.1 255.255.255.240
router bgp 101
network 220.220.16.0 mask 255.255.240.0
neighbor 222.222.10.2 remote-as 100
neighbor 222.222.10.2 prefix-list RouterA in
neighbor 222.222.10.2 prefix-list RouterA out
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Configuring Internal BGP
Router A
interface loopback 0
ip address 215.10.7.1 255.255.255.255
router bgp 100
network 220.220.1.0
neighbor 215.10.7.2 remote-as 100
neighbor 215.10.7.2 update-source loopback0
neighbor 215.10.7.3 remote-as 100
neighbor 215.10.7.3 update-source loopback0
Router B
interface loopback 0
ip address 215.10.7.2 255.255.255.255
router bgp 100
network 220.220.5.0
neighbor 215.10.7.1 remote-as 100
neighbor 215.10.7.1 update-source loopback0
neighbor 215.10.7.3 remote-as 100
neighbor 215.10.7.3 update-source loopback0
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Local Preference
• Configuration of Router B:
router bgp 400
neighbor 220.5.1.1 remote-as 300
neighbor 220.5.1.1 route-map local-pref in
!
route-map local-pref permit 10
match ip address prefix-list MATCH
set local-preference 800
!
ip prefix-list MATCH permit 160.10.0.0/16
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Multi-Exit Discriminator
• Configuration of Router B:
router bgp 400
neighbor 220.5.1.1 remote-as 200
neighbor 220.5.1.1 route-map set-med out
!
route-map set-med permit 10
match ip address prefix-list MATCH
set metric 1000
!
ip prefix-list MATCH permit 192.68.1.0/24
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Inbound and Outbound
router bgp 100
neighbor 220.200.1.1 remote-as 210
neighbor 220.200.1.1 filter-list 5 out
neighbor 220.200.1.1 filter-list 6 in
!
ip as-path access-list 5 permit ^200$
ip as-path access-list 6 permit ^150$
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Example using prefix-lists
router bgp 100
neighbor 1.1.1.1 route-map infilter in
!
route-map infilter permit 10
match ip address prefix-list HIGH-PREF
set local-preference 120
!
route-map infilter permit 20
match ip address prefix-list LOW-PREF
set local-preference 80
!
route-map infilter permit 30
!
ip prefix-list HIGH-PREF permit 10.0.0.0/8
ip prefix-list LOW-PREF permit 20.0.0.0/8
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Example using filter lists
router bgp 100
neighbor 220.200.1.2 route-map filter-on-as-path in
!
route-map filter-on-as-path permit 10
match as-path 1
set local-preference 80
!
route-map filter-on-as-path permit 20
match as-path 2
set local-preference 200
!
route-map filter-on-as-path permit 30
!
ip as-path access-list 1 permit _150$
ip as-path access-list 2 permit _210_
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Example configuration of AS-PATH prepend
router bgp 300
network 215.7.0.0
neighbor 2.2.2.2 remote-as 100
neighbor 2.2.2.2 route-map SETPATH out
!
route-map SETPATH permit 10
set as-path prepend 300 300
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Policy Control:
Example Configuration
router bgp 100
neighbor 220.200.1.2 remote-as 200
neighbor 220.200.1.2 route-map filter-on-community in
!
route-map filter-on-community permit 10
match community 1
set local-preference 50
!
route-map filter-on-community permit 20
match community 2 exact-match
set local-preference 200
!
ip community-list 1 permit 150:3 200:5
ip community-list 2 permit 88:6
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soft reconfiguration:
router bgp 100
neighbor 1.1.1.1 remote-as 101
neighbor 1.1.1.1 route-map infilter in
neighbor 1.1.1.1 soft-reconfiguration inbound
! Outbound does not need to be configured !
Then when we change the policy, we issue an exec command
clear ip bgp 1.1.1.1 soft [in | out]
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Configuring peer group:
router bgp 109
neighbor external-peer peer-group
neighbor external-peer send-community
neighbor external-peer route-map set-metric out
neighbor 160.89.1.2 remote-as 200
neighbor 160.89.1.2 peer-group external-peer
neighbor 160.89.1.4 remote-as 300
neighbor 160.89.1.4 peer-group external-peer
neighbor 160.89.1.6 remote-as 400
neighbor 160.89.1.6 peer-group external-peer
neighbor 160.89.1.6 filter-list infilter in
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router refletor:
router bgp 100
neighbor 1.1.1.1 remote-as 100
neighbor 1.1.1.1 route-reflector-client
neighbor 2.2.2.2 remote-as 100
neighbor 2.2.2.2 route-reflector-client
neighbor 3.3.3.3 remote-as 100
neighbor 3.3.3.3 route-reflector-client
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sub-as
Configuration (rtr B):
router bgp 65532
bgp confederation identifier 200
bgp confederation peers 65530 65531
neighbor 141.153.12.1 remote-as 65530
neighbor 141.153.17.2 remote-as 65531