BGP - [Part 11] - EBGP BASIC CONFIGURATION

BGP - [Part 11] - EBGP BASIC CONFIGURATION

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

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

1. Simple EBGP between two router  -
  • Router1 Configuration - 

Router1#show running-config
interface FastEthernet0/0
 ip address 192.167.23.1 255.255.255.0
 duplex auto
 speed auto
!
router bgp 400
 no synchronization
 bgp log-neighbor-changes
 neighbor 192.167.23.2 remote-as 500
 no auto-summary
  • Router2 Configuration - 

Router2#show running-config
interface FastEthernet0/0
 ip address 192.167.23.2 255.255.255.0
 duplex auto
 speed auto
!
router bgp 500
 no synchronization
 bgp log-neighbor-changes
 neighbor 192.167.23.1 remote-as 400
 no auto-summary

Output - 



2. EBGP 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 500
 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 500
 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. EBGP 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 500
 no auto-summary
!
no ip http server
no ip http secure-server
!
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 500
 no synchronization
 bgp log-neighbor-changes
 neighbor 192.167.23.1 remote-as 400
 no auto-summary
!
no ip http server
no ip http secure-server
!
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. EBGP 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 reach-ability.
  • 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 500
 neighbor 2.2.2.2 ebgp-multihop 2
 neighbor 2.2.2.2 update-source Loopback0
 no auto-summary
!
no ip http server
no ip http secure-server
!
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 500
 no synchronization
 bgp log-neighbor-changes
 neighbor 1.1.1.1 remote-as 400
 neighbor 1.1.1.1 ebgp-multihop 2
 neighbor 1.1.1.1 update-source Loopback0
 no auto-summary

!
no ip http server
no ip http secure-server
!
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. EBGP 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 500
 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 500
 no synchronization
 bgp log-neighbor-changes
 neighbor 192.167.23.1 remote-as 400
 no auto-summary

Output - 

 6. EBGP 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 500
 neighbor 2.2.2.2 ebgp-multihop 2
 neighbor 2.2.2.2 update-source Loopback0
 neighbor 22.22.22.22 remote-as 500
 neighbor 22.22.22.22 ebgp-multihop 2
 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 500
 no synchronization
 bgp log-neighbor-changes
 neighbor 1.1.1.1 remote-as 400
 neighbor 1.1.1.1 ebgp-multihop 2
 neighbor 1.1.1.1 update-source Loopback0
 neighbor 11.11.11.11 remote-as 400
 neighbor 11.11.11.11 ebgp-multihop 2
 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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