NetworkTalk & BGP

B.2.e) Ebgp setup between RT-B and ISP-C upstream link.

1. 3 physical links of ISP-C aggregated as 1 Ebgp neighbor link:

Physical connectivity, loopback and routes:

ip address 30.30.31.22 255.255.255.252
ip address 30.30.31.26 255.255.255.252
ip address 30.30.31.30 255.255.255.252

ISP-A’s loopback ip address: 11.11.226.250 255.255.255.255

ISP-C’s loopback ip address: 30.30.30.127 255.255.255.255

ip route 30.30.30.127 255.255.255.255 POS1/1/2 30.30.31.21 name Loopback-Peer-AS400-ISPC-3xSTM16
ip route 30.30.30.127 255.255.255.255 POS1/1/1 30.30.31.25 name Loopback-Peer-AS400-ISPC-3xSTM16
ip route 30.30.30.127 255.255.255.255 POS1/1/3 30.30.31.29 Loopback-Peer-AS400-ISPC-3xSTM16

2. Ebgp session with ISP-C upstream link:

neighbor 30.30.175.127 remote-as 400
neighbor 30.30.175.127 description ISP-C-Ebgp-Session
neighbor 30.30.175.127 ebgp-multihop 2
neighbor 30.30.175.127 update-source Loopback0
neighbor 30.30.175.127 version 4
!
address-family ipv4
neighbor 30.30.175.127 activate
neighbor 30.30.175.127 send-community both
neighbor 30.30.175.127 route-map AS-400-INCOMING in
neighbor 30.30.175.127 route-map AS-400-OUTGOING out

3. Route-map for downloading full routing table from ISP-C ebgp neighbor and tagged with local pref 90

ip as-path access-list 1 permit ^400_
route-map AS-400-INCOMING permit 10
match as-path 1
set local-preference 90!
// This Internet table received from ISP-C will be tagged with LocalPref 90. However, we desire that ingress/egress traffic of Zone-B leaves through ISP-C Ebgp neighbor. To ensure that, the “next-hop recursive” instruction will be used in order to force the outbound/upload traffic of Zone_B customer to leave though ISP-C.

4. Route-maps for advertising ISP-A’s networks:

Table B-7

4.1) Zone_B ingress traffic: ISP-C Ebgp neighbor as primary link:

 ip prefix-list ZONE_B seq 120 permit 11.11.240.0/24

ip prefix-list ZONE_B seq 280 permit 11.11.255.0/24
route-map AS-400-OUTGOING permit 10
match ip address prefix-list ZONE_B

4.2) ZONE_D_E and ZONE_G will use ISP-C for its ingress traffic as a tertiary backup link

 ip as-path access-list 2 permit ^$
route-map AS-400-OUTGOING permit 20
match as-path 2
set community 400:70
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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