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IBGP Using IPv4 Overlay

This section briefly describes the IBGP using IPv4 overlay feature and its configuration on the QFX5220, QFX5230, QFX5240, and QFX5241 Switches.

Overview

Internal Border Gateway Protocol (IBGP) is a BGP peering type used for routing IPv4 underlay and overlay networks in data center fabrics. IBGP operates within the same autonomous system (AS) as peer devices and requires full-mesh peering or route reflectors to avoid loops. IBGP uses internal peering and shares the same AS number across peers. IBGP sessions often use loopback interfaces (for example, lo0) as the local address for stability in IPv4 fabrics.

Configure IBGP Using IPv4 Overlay

To configure IBGP for the overlay peering in an IPv4 fabric:

  1. Configure an AS number for overlay IBGP. All leaf and spine devices participating in the overlay use the same AS number.

    On spine and leaf devices:

  2. Configure IBGP using EVPN signaling on each spine device to peer with every leaf device. Also, form the route reflector cluster and configure equal-cost multipath (ECMP) for BGP.

    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).

    Leaf 1:

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

Verify IBGP Configuration Using IPv4 Overlay

To verify that IBGP is functional on the spine devices:

To verify that BFD is operational on the spine devices:

To verify that IBGP is operational on the leaf devices:

To verify that BFD is operational on the leaf devices: