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Enabling BGP in ACI fabric

Hello Friends

Today, I will be showing how we can enable BGP in the ACI fabric i.e. between the Spine and the Leaf switches. Between the Spine and the leaf switches, only two protocols are run. One is BGP and the other is ISIS. ISIS is enabled by default. You need to manually configure / enable BGP. The BGP session that we bring up between the Spine and the leaf is MP-BGP session and the Spine nodes always act as a route-reflector. The MP-BGP session is only required for External L3 connections to the ACI fabric. For the internal connections, MP-BGP is not required.

In order to demonstrate how to configure, lets consider the below topology:

 

Follow the below steps to configure MP-BGP session between the Spine and the leaf nodes.

Step 1: Log in into the APIC controller from the web interface and go to the following path:

Fabric > Fabric Policies > Pod Policies > Policies > BGP Route Reflector default.

 

Step 2: Once you select the "BGP Route Reflector default" option, there is a page that gets opened in the right pane. Enter the AS# in the Autonomous System Number field and then click on the (+) icon near the Route Reflector Nodes option.

Step 3: When you click the (+) icon, another popup window gets opened in the same frame which asks to you select the nodes. When you click the drop down list, it will show you all the spine nodes. Select one of the Spine nodes and click Submit.

If you have more than one Spine node, you need to repeat the step 2 again to add another Spine node.

Step 4: Once all the spine nodes are added, Then right click the Policy Groups section and select Create POD Policy Groups.

Step 5: Once we click the Create POD Policy Group link, a popup window opens in the right pane. Put the name of the policy group and select the default value from the drop down list beside BGP Route Reflector policy.

Click Submit.

Step 6: Once done, then go the default option below the Policy Groups section. In the Fabric Policy Group field, Select the Policy Group that we created from the drop down list. This is enable BGP between the leaf and the Spine nodes.

Step 7: Verification - In order to verify the BGP neighborship, Go to the below path to verify the BGP sessions are established.

Fabric > Inventory > Pod1 > Spine1 > Protocols > BGP > overlay-1 > sessions

You will be able to see two BGP neighborships formed for the two leafs. If there are more than one Spine nodes, you will see the same output on both the nodes.

Output on Spine1:
===========
spine1# show bgp sessions vrf overlay-1
Total peers 2, established peers 2
ASN 100
VRF overlay-1, local ASN 100
peers 2, established peers 2, local router-id 10.0.80.94
State: I-Idle, A-Active, O-Open, E-Established, C-Closing, S-Shutdown

Neighbor        ASN    Flaps LastUpDn|LastRead|LastWrit St Port(L/R)  Notif(S/R)
10.0.80.92       100 0     00:24:16|never   |never    E  179/53171  0/0
10.0.80.95       100 0     00:24:16|never   |never    E  179/44003  0/0
spine1# 

Output on Leaf1:
===========
leaf1# show bgp sessions vrf overlay-1
Total peers 1, established peers 1
ASN 100
VRF overlay-1, local ASN 100
peers 1, established peers 1, local router-id 10.0.80.95
State: I-Idle, A-Active, O-Open, E-Established, C-Closing, S-Shutdown

Neighbor        ASN    Flaps LastUpDn|LastRead|LastWrit St Port(L/R)  Notif(S/R)
10.0.80.94       100 0     00:22:52|never   |never    E  44003/179  0/0
leaf1#

Thus from the above output we can see that both the BGP sessions are formed.

Hope this helps you enable BGP in the ACI fabric.

Please feel free to reach out to us in case of any queries.

Cheers..!!!

Genie
www.codergenie.com

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