BGP Lab 6 eBGP Neighborship (CCNP Level)


Download Lab: GNS3

Image requirements:
 Cisco IOSv        (vios-adventerprisek9-m.vmdk.SPA.156-2.T)


Introduction:
This lab advances your skills with eBGP as you continue to learn more, you will understand that most of the time routers who need to talk BGP establish their neighbor relation by using loopback interfaces, simple example when there are multiple links between a set of routers they only able to form one bgp session, but in order to utilize both connections for redundancy purpose use loopback interfaces for bgp sessions and then configure equal-cost multipath between two routers to reach IP addresses of loopbacks.

Lab tasks:

1. Configure eBGP session between AS250 router ER1 and AS101 router ISP1 using their respective Loopback0 interfaces as shown in the topology. In order to establish eBGP neighborship, you have to also specify as the source of bgp updates the interface Loopback0, and be aware of default eBGP behavior when using the Loopback interfaces, it is necessary to modify TTL field in the BGP packet to more than the default of 1, with ebgp-multihop command. When configuring BGP assign to the routers bgp router-id of their loopback interfaces.

2. Follow the same principle as explained in the step1 configure eBGP session between AS250 router ER1 and AS102 router ISP2.

3. Configure eBGP session between AS250 router ER2 and AS101 router ISP1, using their respective Loopback0 interfaces.

4. Configure eBGP session between AS250 router ER2 and AS102 router ISP2, using their respective Loopback0 interfaces.

5. Configure eBGP session between AS101 router ISP1 and AS102 router ISP2, using their respective Loopback0 interfaces.

6. Configure eBGP session between AS101 router ISP1 and AS103 router ISP3, using their respective Loopback0 interfaces.

7. Configure eBGP session between AS101 router ISP1 and AS104 router ISP4, using their respective Loopback0 interfaces.

8. Configure eBGP session between AS102 router ISP2 and AS103 router ISP3, using their respective Loopback0 interfaces.

9. Configure eBGP session between AS103 router ISP3 and AS104 router ISP4, using their respective Loopback0 interfaces.

10. Check all eBGP neighborship formation by using verification commands you learned from your study.

11. Save configurations on all routers.


Configuration example:
!
ER1(config)# router bgp 250
ER1(config-router)# bgp router-id 20.0.0.251
ER1(config-router)# neighbor 50.0.0.100 remote-as 101
ER1(config-router)# neighbor 50.0.0.100 update-source lo0
ER1(config-router)# neighbor 50.0.0.100 ebgp-nultihop 2
ER1(config-router)# end

Verify the eBGP session:
!
ER1# show  ip bgp summary
ER1# show ip bgp neighbors
ER1# show tcp brief
ER1# debug ip bgp

Verify the eBGP table:
!
ER1# show ip bgp

Administratively control neighbor status:
!
ER1(config)# router bgp 250
ER1(config-router)# neighbor 50.0.0.100 shutdown 


Topology:

 

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