BGP - [Part 7] - NEXT HOP SELF

With Next Hop Self

Now we will advertise the network for point to point reach-ability and will use "next-hop-self" command to change IBGP behavior regarding next hop (When an update send within the same AS - Next hop will be same)

Below is the new Configuration -

R1 Configuration - 
interface FastEthernet0/0
 ip address 192.167.22.1 255.255.255.0
 duplex auto
 speed auto
!
router bgp 100
 no synchronization
 bgp log-neighbor-changes
 network 192.167.22.0
 neighbor 192.167.22.2 remote-as 100
 no auto-summary

R2 Configuration - 
interface FastEthernet0/0
 ip address 192.167.22.2 255.255.255.0
 duplex auto
 speed auto
!
interface FastEthernet1/0
 ip address 192.167.23.1 255.255.255.0
 duplex auto
 speed auto
!
router bgp 100
 no synchronization
 bgp log-neighbor-changes
 network 192.167.23.0
 neighbor 192.167.22.1 remote-as 100
 neighbor 192.167.22.1 next-hop-self
 neighbor 192.167.23.2 remote-as 200
 no auto-summary

R3 Configuration - 
interface FastEthernet1/0
 ip address 192.167.23.2 255.255.255.0
 duplex auto
 speed auto
!
interface FastEthernet2/0
 ip address 192.167.24.1 255.255.255.0
 duplex auto
 speed auto
!
router bgp 200
 no synchronization
 bgp log-neighbor-changes
 network 192.167.24.0
 neighbor 192.167.23.1 remote-as 100
 neighbor 192.167.24.2 remote-as 300
 no auto-summary

R4 Configuration - 
interface Loopback1
 ip address 1.1.1.1 255.255.255.0
!
interface FastEthernet2/0
 ip address 192.167.24.2 255.255.255.0
 duplex auto
 speed auto
!
router bgp 300
 no synchronization
 bgp log-neighbor-changes
 network 1.1.1.0 mask 255.255.255.0
 neighbor 192.167.24.1 remote-as 200
 no auto-summary

Now in R1, R2 and R3 we have advertised the network and configured the next-hop-self

Verification - 

Now we will verify -

Now R1 learns the prefix and installed it in the routing table and R1 has next hop 192.167.22.2 for network 1.1.1.0/24, it means next hop has been changed due to "next-hop-self" command

Now we have point to point reach-ability, we can ping network 1.1.1.0/24 from R1, R2 and R3 router.

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Anubhav Upadhyay

Hello and welcome to networktopic Blog. My name is Anubhav. I am a Senior Network Egineer. I have created this blog specially to serve interview questions and answer on Network Routing and Switching, I will try my best to serve correct and updated networking knowledge for you as per my corporate experience.

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