Di Posting Oleh : Simple Learning
Kategori : BGP Core Technologies Routing
Prerequisites: CCNP level skills.
Topology
Task 1
Ensure reachability between 172.16.102.0/24 and 172.16.105.0/24.
Lab Solution
Task 1
Ensure reachability between 172.16.102.0/24 and 172.16.105.0/24.
Since IBGP Split-Horizon rule forbids to advertise prefixes learned from IBGP peer to another IBGP peer, R1 does not forward 172.16.102.0/24 to R5 and 172.16.105.0/24 to R2. There are two solutions to this problem:
- Route-Reflector configuration on R1 (disabling IBGP Split-Horizon)
- Configure BGP Confederations
In order to implement BGP confederations BGP routing on R1, R3 and R4 must be reconfigured entirely.
R2 and R5 BGP configuration remains the same (Lab 93).
R1 Configuration:
!
router bgp 65014
no synchronization
bgp router-id 172.16.101.1
bgp log-neighbor-changes
bgp confederation identifier 134
bgp confederation peers 65003
neighbor 10.1.13.3 remote-as 65003
neighbor 10.1.14.4 remote-as 65014
no auto-summary
no synchronization
bgp router-id 172.16.101.1
bgp log-neighbor-changes
bgp confederation identifier 134
bgp confederation peers 65003
neighbor 10.1.13.3 remote-as 65003
neighbor 10.1.14.4 remote-as 65014
no auto-summary
!
R3 Configuration:
!
router bgp 65003
no synchronization
bgp router-id 172.16.103.3
bgp log-neighbor-changes
bgp confederation identifier 134
bgp confederation peers 65014
neighbor 10.1.13.1 remote-as 65014
no synchronization
bgp router-id 172.16.103.3
bgp log-neighbor-changes
bgp confederation identifier 134
bgp confederation peers 65014
neighbor 10.1.13.1 remote-as 65014
neighbor 10.1.13.1 next-hop-self
neighbor 10.1.35.5 remote-as 50
no auto-summary
neighbor 10.1.35.5 remote-as 50
no auto-summary
!
R4 Configuration:
!
router bgp 65014
no synchronization
bgp router-id 172.16.104.4
bgp log-neighbor-changes
bgp confederation identifier 134
neighbor 10.1.14.1 remote-as 65014
neighbor 10.1.14.1 next-hop-self
neighbor 10.1.24.2 remote-as 20
no auto-summary
no synchronization
bgp router-id 172.16.104.4
bgp log-neighbor-changes
bgp confederation identifier 134
neighbor 10.1.14.1 remote-as 65014
neighbor 10.1.14.1 next-hop-self
neighbor 10.1.24.2 remote-as 20
no auto-summary
!
Notice!
The next-hop attribute behaves like in a regular EBGP-to-IBGP sessions. Confederation EBGP does NOT modify the next-hop attribute hence the next-hop-self command on R3 and R4.
Verification:
Pic. 2 - R3's BGP Table.
Pic. 3 - R4's BGP Table.
Pic. 4 - R2's BGP Table.
Notice!
The Private AS numbers are stripped off while advertising prefixes to real EBGP peers.
Pic. 5 - Ping Test.
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