NetworkTalk & BGP

B.2.f) Ebgp setup between RT-B and ISP-B transit/upstream link.

1. Ebgp session with ISP-B:

 neighbor 20.20.20.85 remote-as 300
neighbor 20.20.20.85 description ISP-B-Ebgp-Session
neighbor 20.20.20.85 version 4
neighbor 20.20.20.85 send-community both
neighbor 20.20.20.85 route-map AS-300-OUTGOING out

 2. Route-map for downloading BGP table(set as best LocalpRef 100) from ISP-B.

ip as-path access-list 3 permit ^300_
route-map AS-300-INCOMING permit 10
match as-path 3

3. Route-maps for advertising ISP-B’s networks:

Table B-8

3.1) Zone_G ingress traffic: ISP-B Ebgp neighbor as primary link:

ip prefix-list ZONE_G seq 40 permit 11.11.230.0/24
ip prefix-list ZONE_G seq 50 permit 11.11.231.0/24

ip prefix-list ZONE_G seq 130 permit 11.11.238.0/24
ip prefix-list ZONE_G seq 140 permit 11.11.239.0/24
ip prefix-list ZONE_G seq 200 permit 10.10.192.0/24
ip prefix-list ZONE_G seq 210 permit 10.10.193.0/24

ip prefix-list ZONE_G seq 310 permit 10.10.203.0/24
ip prefix-list ZONE_G seq 320 permit 10.10.204.0/24
route-map AS-300-OUTGOING permit 10
match ip address prefix-list ZONE_G

3.2) ZONE_D_E , ZONE_B will use ISP-B Ebgp neighbor for its ingress traffic as a secondary link

ip prefix-list ZONE_B seq 120 permit 11.11.240.0/24
ip prefix-list ZONE_B seq 130 permit 11.11.241.0/24

ip prefix-list ZONE_B seq 270 permit 11.11.254.0/24
ip prefix-list ZONE_B seq 280 permit 11.11.255.0/24
!
ip prefix-list ZONE_D_E seq 30 permit 10.10.205.0/24
ip prefix-list ZONE_D_E seq 40 permit 10.10.206.0/24
ip prefix-list ZONE_D_E seq 50 permit 10.10.207.0/24
ip prefix-list ZONE_D_E seq 60 permit 11.11.229.0/24
route-map AS-300-OUTGOING permit 20
match ip address prefix-list ZONE_B
set community 300:80
!
route-map AS-300-OUTGOING permit 30
match ip address prefix-list ZONE_D_E
set community 300:80

3.3) The rest of ISP-A’s network will use ISP-B link as a 3rd backup link

ip as-path access-list 2 permit ^$
route-map AS-300-OUTGOING permit 20
match as-path 2
set community 300:70
Note: “match as-path 2” instruction includes also the networks block 10.10.192.0/20 and 11.11.224.0/19 for the redundancy aggregation purposes.

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