Cisco Configuring Optimized Layer 2 Overlay Multicast: Руководство по настройке и обслуживанию

Information About Optimized Layer 2 Overlay Multicast

Configuring Optimized Layer 2 Overlay Multicast Restrictions for Optimized Layer 2 Overlay Multicast, on page 1 Information About Optimized Layer 2 Overlay Multicast, on page 1 How to Configure Optimized Layer 2 Overlay Multicast, on page 5 Verifying Optimized Layer 2 Overlay Multicast on VTEP and Centralized Gateway, on page 9 Configuration Examples for Optimized Layer 2 Overlay Multicast, on page 10 Restrictions for Optimized Layer 2 Overlay Multicast • This feature does not support data MDT in the underlay. • Optimized Layer 2 overlay multicast source specific forwarding (S,G) is not supported. Only (*,G) is supported.

• Optimized Layer 2 overlay multicast is ineffective for a Distributed Anycast Gateway deployment (use Layer 3 Tenant Routed Multicast in a Distributed Anycast Gateway deployment). Optimized Layer 2 overlay multicast is applicable between Layer 2 Leaf or Centralized Gateway that extends the bridge-domain over EVPN VXLAN fabric. • Optimized Layer 2 overlay multicast handoff to Layer 3 tenant routed multicast (TRM) within the EVPN fabric is not supported. Information About Optimized Layer 2 Overlay Multicast Optimized Layer 2 Overlay Multicast functionality is based on IGMP or MLD Proxy for EVPN, as defined in draft-ietf-bess-evpn-igmp-mld-proxy .

In a BGP EVPN VXLAN fabric, there can be many hosts attached to a VLAN that is stretched across several sites. These hosts send IGMP membership reports to join their interested multicast groups. Also, the IGMP router periodically sends membership queries to find out if there are hosts on a VLAN that are interested in receiving multicast traffic for that group. This leads to a flooding of IGMP reports and queries in the overlay network across multiple sites. The network may have few hosts but the IGMP messages are sent to all VTEPs, resulting in an overloading of the fabric. This necessitates an IGMP or MLD Proxy to efficiently forward the multicast traffic.

When you enable an IGMP or MLD Proxy on the VTEP, the proxy forwards the multicast traffic only to the interested receivers, thus optimizing the bandwidth of the fabric. Configuring Optimized Layer 2 Overlay Multicast 1

Page 1

Optimized Layer 2 Multicast in BGP EVPN VXLAN Layer 2 Overlay

Optimized Layer 2 Overlay Multicast functionality facilitates multicast traffic both at the access level and within the VXLAN fabric. Optimized Layer 2 Overlay Multicast is restricted to a Layer 2 Virtual Network Instance (L2VNI), wherein the source and receivers are within the same Layer 2 domain. Layer 2 multicast data traffic is not forwarded to a VTEP or a port that does not have a multicast router or receiver attached to it. Optimized Layer 2 Overlay Multicast supports both IPv4 and IPv6 multicast traffic in a Layer 2 EVPN VXLAN fabric.

Optimized Layer 2 Multicast in BGP EVPN VXLAN Layer 2 Overlay Optimized Layer 2 Overlay Multicast uses an EVPN instance (EVI) to build an IGMP or MLD overlay. When a VTEP receives an IGMP or MLD report from a host on the access link, it propagates this information to all other VTEPs in the same EVI, using EVPN Route Type 6 (RT6). Propagation of RT6 updates the multicast forwarding tree for the intra-VLAN multicast traffic in the fabric. If a host on a second VTEP sends multicast traffic to a group that already has receivers, traffic is forwarded in the established multicast forwarding tree.

Multicast traffic source and receiver, which are on the same VLAN but stretched across VTEPs in the BGP EVPN VXLAN fabric, can communicate with each other. Source and Receiver on Same VLAN, Connected to Different Layer 2 VTEPs Figure 1: Topology to show Layer 2 Overlay Multicast Traffic within a VLAN 1. Receiver R3 in VLAN 10 sends (*,G) IGMP Join to VTEP 2. (*,G) is created at VTEP 2. 2. VTEP 2 sends EVPN route type 6 to VTEP 1. (*,G) is created at VTEP 1. Configuring Optimized Layer 2 Overlay Multicast Optimized Layer 2 Multicast in BGP EVPN VXLAN Layer 2 Overlay Configuring Optimized Layer 2 Overlay Multicast 2

Page 2

Optimized Layer 2 Multicast across Layer 2 Overlays

3. Source S1 in VLAN 10 starts streaming data. VTEP 1 forwards the multicast packets to all other VTEPs that have receivers. 4. Layer 2 multicast packets are encapsulated with L2VNI that corresponds to VLAN 10 and are forwarded through the overlay to VTEP 2. 5. On VTEP 2, the L2VNI encapsulated data packets are decapsulated and forwarded to the port where receiver R3 is connected. Optimized Layer 2 Overlay Multicast Interworking in BGP EVPN VXLAN Fabric VTEPs in the EVPN VXLAN network forward traffic to each other through the VXLAN gateways. An EVPN VXLAN Centralized Gateway (CGW) VTEP performs the Layer 3 gateway function for all the Layer 2 VNIs.

All the other VTEPs in the network perform only bridging. For information on CGW, see “Configuring EVPN VXLAN Integrated Routing and Bridging”. Optimized Layer 2 Multicast across Layer 2 Overlays In an EVPN VXLAN fabric, a CGW performs routing for the inter-L2VNI Layer 2 multicast traffic. In this case, the sender and receiver, both could be on the same VTEP or they could be on different VTEPs within the EVPN VXLAN fabric. Source and Receiver on Different VLANs, connected to Different Layer 2 VTEPs Figure 2:

Topology to show Layer 2 Overlay Multicast Traffic between Different VLANs Configuring Optimized Layer 2 Overlay Multicast Optimized Layer 2 Overlay Multicast Interworking in BGP EVPN VXLAN Fabric Configuring Optimized Layer 2 Overlay Multicast 3

Page 3

Optimized Layer 2 Overlay Multicast Handoff with External Network

1. CGW sends EVPN route type 6 (*, *) to all the Layer 2 VTEPs in EVPN VXLAN fabric. 2. Receiver R4 in VLAN 20 sends (*, G) IGMP join to VTEP 2. (*, G) is created in IGMP snooping table on VTEP 2. 3. VTEP 2 sends EVPN route type 6 (*, G) to the CGW and all other Layer 2 VTEPs. (* , G) is also created in Layer 3 multicast on the CGW. 4. Source S1 in VLAN 10 starts streaming data. VTEP1 forwards the multicast traffic. 5. Layer 2 multicast traffic is switched through L2VNI to the CGW, based on the default EVPN route type 6. In the CGW, multicast data packets are processed by Layer 3 Multicast and routed to access SVI20 where the receiver R4 is connected. 6.

Multicast traffic is forwarded to VTEP 2 through L2VNI. On egress VTEP 2, Layer 2 Overlay Multicast switches the data packets to the port where the receiver R4 is connected. Optimized Layer 2 Overlay Multicast Handoff with External Network Figure 3: Topology to show Layer 2 Overlay Multicast Traffic Handoff to an External Network In this topology, either the multicast receiver or sender exists on an external network. The Centralized Gateway is configured to route the multicast traffic between the EVPN VXLAN fabric and the external network. The leaf VTEPs in the VXLAN fabric perform only bridging.

If a source device that is connected to a Layer 2 VTEP starts streaming multicast traffic, the traffic is bridged from the Layer 2 VTEP to the Centralized Gateway VTEP. The Centralized Gateway VTEP then routes the multicast traffic to the interested receivers in the external network. The Rendezvous Point (RP) is located outside the fabric. Configuring Optimized Layer 2 Overlay Multicast Optimized Layer 2 Overlay Multicast Handoff with External Network Configuring Optimized Layer 2 Overlay Multicast 4

Page 4