Configuring IBGP for the Overlay

For a control-plane driven overlay, there must be a signalling path between all VTEP devices within an autonomous system using IBGP with Multiprotocol BGP (MP-IBGP). In this reference design, all overlay types use IBGP, the spine devices act as a route reflector cluster, and the leaf devices are route reflector clients, as shown in Figure 1.

Figure 1: IBGP Route Reflector Cluster

1. Configure an AS number for overlay IBGP. All leaf and spine devices participating in the overlay use the same AS number. In this example, the AS number is private AS 4210000001.

   Spine and Leaf Devices:
2. Configure IBGP using EVPN signaling on each spine device to peer with every leaf device (Leaf 1 through Leaf 96). Also, form the route reflector cluster (cluster ID 192.168.0.10) and configure equal cost multipath (ECMP) for BGP. The configuration included here belongs to Spine 1, as shown in Figure 2.

   Figure 2: IBGP – Spine Device

   

   Tip

   By default, BGP selects only one best path when there are multiple, equal-cost BGP paths to a destination. When you enable BGP multipath by including the multipath statement at the [edit protocols bgp group group-name] hierarchy level, the device installs all of the equal-cost BGP paths into the forwarding table. This feature helps load balance the traffic across multiple paths.

   Spine 1:
3. Configure IBGP on the spine devices to peer with all the other spine devices acting as route reflectors. This step completes the full mesh peering topology required to form a route reflector cluster.

   Spine 1:
4. Configure BFD on all BGP groups on the spine devices to enable rapid detection of failures and reconvergence.

   Spine 1:
5. Configure IBGP with EVPN signaling from each leaf device (route reflector client) to each spine device (route reflector cluster). The configuration included here belongs to Leaf 1, as shown in Figure 3.

   Figure 3: IBGP – Leaf Device

   

   Leaf 1:
6. Configure BFD on the leaf devices to enable rapid detection of failures and reconvergence.

   Leaf 1:
7. Verify that IBGP is functional on the spine devices.
   user@spine-1> show bgp summary
8. Verify that BFD is operational on the spine devices.
   user@spine-1> show bfd session
9. Verify that IBGP is operational on the leaf devices.
   user@leaf-1> show bgp summary
10. Verify that BFD is operational on the leaf devices.
    user@leaf-10> show bfd session