BGP - [Part 10] - IBGP BASIC CONFIGURATION

BGP - [Part 10] - IBGP BASIC CONFIGURATION

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Question - 1 How can we configure IBGP between two router ?

We can configure IBGP in multiple way, so before starting the BGP configuration you should know the below basic IBGP concept, it will be helpful.

1. Simple IBGP between two router  - 

  • Router1 Configuration-

Router1#show running-config
interface FastEthernet0/0
 ip address 192.167.23.1 255.255.255.0
 speed 100
 full-duplex
!
router bgp 400
 no synchronization
 bgp log-neighbor-changes
 neighbor 192.167.23.2 remote-as 400
 no auto-summary
  • Router2 Configuration-

Router2#show running-config
interface FastEthernet0/0
 ip address 192.167.23.2 255.255.255.0
 speed 100
 full-duplex
!
router bgp 400
 no synchronization
 bgp log-neighbor-changes
 neighbor 192.167.23.1 remote-as 400
 no auto-summary

Output-


2. IBGP with Loop-back network advertisement - 

For the loop-back reachability, you will have to advertise loop-back network under the BGP
  • Router1 Configuration-
Router1#show running-config
interface Loopback0
 ip address 1.1.1.1 255.255.255.0
!
interface Loopback1
 ip address 11.11.11.11 255.255.255.0
!
interface FastEthernet0/0
 ip address 192.167.23.1 255.255.255.0
 speed 100
 full-duplex
!
router bgp 400
 no synchronization
 bgp log-neighbor-changes
 network 1.1.1.0 mask 255.255.255.0
 network 11.11.11.0 mask 255.255.255.0
 neighbor 192.167.23.2 remote-as 400
 no auto-summary

  • Router2 Configuration-
Router2#show running-config
interface Loopback0
 ip address 2.2.2.2 255.255.255.0
!
interface Loopback1
 ip address 22.22.22.22 255.255.255.0
!
interface FastEthernet0/0
 ip address 192.167.23.2 255.255.255.0
 speed 100
 full-duplex
!
router bgp 400
 no synchronization
 bgp log-neighbor-changes
 network 2.2.2.0 mask 255.255.255.0
 network 22.22.22.0 mask 255.255.255.0
 neighbor 192.167.23.1 remote-as 400
 no auto-summary

Output-


3. IBGP with Static Route (Method 1) - 
You can also use the static route or other IGP routing protocol for loop-back network reachability, instead of loop-back network advertisement.
  • Router1 Configuration - 
Router1#show running-config
interface Loopback0
 ip address 1.1.1.1 255.255.255.0
!
interface Loopback1
 ip address 11.11.11.11 255.255.255.0
!
interface FastEthernet0/0
 ip address 192.167.23.1 255.255.255.0
 speed 100
 full-duplex
!
router bgp 400
 no synchronization
 bgp log-neighbor-changes
 neighbor 192.167.23.2 remote-as 400
 no auto-summary
!
ip forward-protocol nd
ip route 2.2.2.0 255.255.255.0 192.167.23.2
ip route 22.22.22.0 255.255.255.0 192.167.23.2

  • Router2 Configuration - 

Router2#show running-config
interface Loopback0
 ip address 2.2.2.2 255.255.255.0
!
interface Loopback1
 ip address 22.22.22.22 255.255.255.0
!
interface FastEthernet0/0
 ip address 192.167.23.2 255.255.255.0
 speed 100
 full-duplex
!
router bgp 400
 no synchronization
 bgp log-neighbor-changes
 neighbor 192.167.23.1 remote-as 400
 no auto-summary
!
ip forward-protocol nd
ip route 1.1.1.0 255.255.255.0 192.167.23.1
ip route 11.11.11.0 255.255.255.0 192.167.23.1

Output - 

4. IBGP with Static IP (Method 2) - 
You can also establish the neighbor-ship via loop-back network, but you will have to use static route or other IGP routing protocol for loop-back network reachability.
  • Router1 Configuration
Router1#show running-config
interface Loopback0
 ip address 1.1.1.1 255.255.255.0
!
interface Loopback1
 ip address 11.11.11.11 255.255.255.0
!
interface FastEthernet0/0
 ip address 192.167.23.1 255.255.255.0
 speed 100
 full-duplex
!
router bgp 400
 no synchronization
 bgp log-neighbor-changes
 neighbor 2.2.2.2 remote-as 400
 neighbor 2.2.2.2 update-source Loopback0
 no auto-summary
!
ip forward-protocol nd
ip route 2.2.2.0 255.255.255.0 192.167.23.2
ip route 22.22.22.0 255.255.255.0 192.167.23.2
  • Router2 Configuration

Router2#show running-config
interface Loopback0
 ip address 2.2.2.2 255.255.255.0
!
interface Loopback1
 ip address 22.22.22.22 255.255.255.0
!
interface FastEthernet0/0
 ip address 192.167.23.2 255.255.255.0
 speed 100
 full-duplex
!
router bgp 400
 no synchronization
 bgp log-neighbor-changes
 neighbor 1.1.1.1 remote-as 400
 neighbor 1.1.1.1 update-source Loopback0
 no auto-summary
!
ip forward-protocol nd
ip route 1.1.1.0 255.255.255.0 192.167.23.1
ip route 11.11.11.0 255.255.255.0 192.167.23.1

 Output - 

5. IBGP with OSPF (Method-1)- 
Here we are using OSPF for loop-back network reachability. 
  • Router1 Configuration - 
Router1#show running-config
interface Loopback0
 ip address 1.1.1.1 255.255.255.0
!
interface Loopback1
 ip address 11.11.11.11 255.255.255.0
!
interface FastEthernet0/0
 ip address 192.167.23.1 255.255.255.0
 speed 100
 full-duplex
!
router ospf 1
 log-adjacency-changes
 network 1.1.1.0 0.0.0.255 area 0
 network 11.11.11.0 0.0.0.255 area 0
 network 192.167.23.0 0.0.0.255 area 0
!
router bgp 400
 no synchronization
 bgp log-neighbor-changes
 neighbor 192.167.23.2 remote-as 400
 no auto-summary
  • Router2 Configuration - 

Router2#show running-config
interface Loopback0
 ip address 2.2.2.2 255.255.255.0
!
interface Loopback1
 ip address 22.22.22.22 255.255.255.0
!
interface FastEthernet0/0
 ip address 192.167.23.2 255.255.255.0
 speed 100
 full-duplex
!
router ospf 1
 log-adjacency-changes
 network 2.2.2.0 0.0.0.255 area 0
 network 22.22.22.0 0.0.0.255 area 0
 network 192.167.23.0 0.0.0.255 area 0
!
router bgp 400
 no synchronization
 bgp log-neighbor-changes
 neighbor 192.167.23.1 remote-as 400
 no auto-summary

Output - 


5. IBGP with OSPF (Method-2)-
  • Router1 Configuration - 
Router1#show running-config
interface Loopback0
 ip address 1.1.1.1 255.255.255.0
!
interface Loopback1
 ip address 11.11.11.11 255.255.255.0
!
interface FastEthernet0/0
 ip address 192.167.23.1 255.255.255.0
 speed 100
 full-duplex
!
router ospf 1
 log-adjacency-changes
 network 1.1.1.0 0.0.0.255 area 0
 network 11.11.11.0 0.0.0.255 area 0
 network 192.167.23.0 0.0.0.255 area 0
!
router bgp 400
 no synchronization
 bgp log-neighbor-changes
 neighbor 2.2.2.2 remote-as 400
 neighbor 2.2.2.2 update-source Loopback0
 neighbor 22.22.22.22 remote-as 400
 neighbor 22.22.22.22 update-source Loopback1
 no auto-summary
  • Router2 Configuration - 
Router2#show running-config
interface Loopback0
 ip address 2.2.2.2 255.255.255.0
!
interface Loopback1
 ip address 22.22.22.22 255.255.255.0
!
interface FastEthernet0/0
 ip address 192.167.23.2 255.255.255.0
 speed 100
 full-duplex
!
router ospf 1
 log-adjacency-changes
 network 2.2.2.0 0.0.0.255 area 0
 network 22.22.22.0 0.0.0.255 area 0
 network 192.167.23.0 0.0.0.255 area 0
!
router bgp 400
 no synchronization
 bgp log-neighbor-changes
 neighbor 1.1.1.1 remote-as 400
 neighbor 1.1.1.1 update-source Loopback0
 neighbor 11.11.11.11 remote-as 400
 neighbor 11.11.11.11 update-source Loopback1
 no auto-summary

Output - 

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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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