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Multicast Optimization in an Edge-Routed Bridging Overlay Design and Implementations

 

Use this design to configure multicast optimizations in your edge-routed bridging overlay. This design assumes that edge-routed bridging model of EVPN-VXLAN is already running for IPv4. See Edge-Routed Bridging Overlay Design and Implementation for information about configuring edge-routed bridging.

This configuration shows multicast optimization in an edge-routed bridging design, but these features are also supported in a centrally routed bridging overlay.

This section shows how to add multicast optimizations to the topology shown in Figure 1.

Figure 1: Toplology for Multicast Optimizations in an Edge-Routed Bridging Overlay
Toplology for Multicast Optimizations in an Edge-Routed Bridging Overlay

Multicast is configured as follows:

  • Server leaf devices are set up in AR client role and for IGMP snooping.

  • Spine devices are set up in AR replicator role.

  • Border leaf devices are set up for multicast routing.

For an overview of multicast optimizations, see the Multicast Optimization section in Data Center Fabric Blueprint Architecture Components.

The following sections show how to configure and verify multicast assisted replication:

Configuring the Server Leaf

We are configuring AR and IGMP snooping on the server leaf. When IGMP snooping is enabled on a device, SMET is also enabled on the device by default.

  1. Enable IGMP snooping.
  2. Enable AR in the client (leaf) role. This causes the server leaf to only forward one copy of multicast traffic to the spine, which then performs replication of the multicast traffic.

Configuring the Spine

We are configuring the spine as AR replicator device.

  1. Configure IP addressing for the loopback interfaces. One address is used for the AR replicator role (192.168.102.2). The other address (192.168.2.2) is used for the VTEP tunnel.
  2. Configure the spine to act as the AR replicator device.
  3. Configure the loopback interface that is used in the VRF routing instance.
  4. Configure a VRF routing instance.
  5. Configure VLANs to the border leaf.
  6. Configure the EVPN protocol with VXLAN encapsulation.
  7. Configure the switch options, and specify that the loopback interface is the VTEP source interface.

Configuring the Border Leaf

The border leaf performs multicast routing. AR is not configured on the border leaf in this example, but you can enable AR on the border leaf.

  1. Configure VLANs
  2. Configure the EVPN protocol with VXLAN encapsulation.
  3. Configure the switch options and specify that the loopback interface is the VTEP source interface.
  4. Configure the IRBs.
  5. Configure a VRF routing instance.
  6. Configure PIM for multicast routing at the border leaf devices.

Verifying Assisted Replication on the Server Leaf

The server leaf is in the role of AR client (leaf) device. This means that it does not perform ingress replication. Instead, it forwards one copy of multicast traffic to the spine, which is configured as the AR replicator device.

  1. Verify the spine that is set up as the AR device for the VLAN. 192.168.102.2 is the address of the AR device.
    user@server-leaf> show evpn multicast-snooping assisted-replication next-hops l2-domain-id 100001
  2. 2. Verify that the spines are in the role of Assisted Replicator and are receiving Type 3 routes. Address 192.168.102.1 is Spine 1, and address 192.168.102.2 is Spine 2.
    user@server-leaf> show route table bgp.evpn.0 match-prefix 3:*100001*192.168.102.* extensive | match "3:192.168.2|ASSISTED-REPLICATION"
    user@server-leaf> show route table bgp.evpn.0 match-prefix 3:*100001*192.168.102.1* extensive
  3. Verify the flood next hop on the leaf. The leaf should send traffic to the spine that is the assisted replicator, and to its leaf peer (192.168.0.2).
    user@server-leaf> show ethernet-switching flood vlan-name BD-1 extensive
  4. Verify the VTEP to leaf 2. Address 192.168.0.2 is the address of Leaf 2.
    user@server-leaf> show interfaces vtep.32838

Verifying Assisted Replication on the Spine

  1. Verify the leaf devices that are AR client (leaf) devices, which in this case are the server leaf devices. The border leaf devices are not set up for assisted replication.
    user@spine> show route table bgp.evpn.0 match-prefix 3:*100001*192.168.0.* extensive | match "3:192.168.0.|LEAF"| except "PMSI|Path"
    user@spine> show route table bgp.evpn.0 match-prefix 3:*100001*192.168.0.1 extensive

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