Layer 3 VSN with IP Multicast over Fabric Connect

IP Multicast over Fabric Connect supports Layer 3 VSN functionality where multicast traffic is bridged over the SPBM core infrastructure. Layer 3 VSN using IP Multicast over Fabric Connect is helpful when you need complete security and total isolation of data. No one outside of the Layer 3 VSN can join or even see the Layer 3 VSN. Applications that can use Layer 3 VSN with IP Multicast over Fabric Connect include: Video surveillance, TV/Video/Ticker/Image Distribution, VX-LAN, Multi-tenant IP multicast.

Configure the Layer 3 VSN (VRF) as a multicast VPN, and then enable IP Multicast over Fabric Connect on VRF VLANs to which IP multicast senders and receivers attach. This configuration automatically enables IGMP snooping and proxy on those VLANs. IGMPv2 at the VLAN level is the default setting, with no other configuration required. If you want to use IGMPv3, you must configure IGMPv3.

IP Multicast over Fabric Connect is only configured on BEBs.

Note

Note

I-SIDs

With Layer 3 VSN with IP Multicast over Fabric Connect, multicast traffic remains in the same Layer 3 VSN across the SPBM cloud. For a Layer 3 VSN, traffic can cross VLAN boundaries but remains confined to the subset of VLANs within the VRF that has IP Multicast over Fabric Connect enabled. If a sender transmits a multicast stream to a BEB on a Layer 3 VSN with IP Multicast over Fabric Connect enabled, only receivers that are part of the same Layer 3 VSN can receive that stream.

After a BEB receives IP multicast data from a sender, the BEB allocates a data service instance identifier (I-SID) in the range of 16,000,000 to 16,512,000 for the multicast stream. The stream is identified by the S, G, V tuple, which is the source IP address, the group IP address and the local VLAN the multicast stream is received on. The data I-SID uses Tx/Rx bits to signify whether the BEB uses the I-SID to transmit, receive, or both transmit and receive data on that I-SID.

In the context of Layer 3 VSNs with IP Multicast over Fabric Connect, the scope is the I-SID value of the Layer 3 VSN associated with the local VLAN that the IP multicast data was received on.

TLVs

This information is propagated through the SPBM cloud using IS-IS Link State Packets (LSPs), which carry TLV updates, that result in the multicast tree creation for that stream. For Layer 3 VSNs, the LSPs carry I-SID information and information about where IP multicast stream senders and receivers exist using TLV 144 and TLV 185.

IS-IS acts dynamically using the TLV information received from BEBs that connect to the sender and the receivers to create a multicast tree between them.

IGMP

After a BEB receives an IGMP join message from a receiver, the BEB queries the IS-IS database to check if a sender exists for the requested stream within the scope of the receiver. If the requested stream does not exist, the IGMP information is kept, but no further action is taken. If the requested stream exists, the BEB sends an IS-IS TLV update to its neighbors to inform them of the presence of a receiver and this information is propagated through the SPBM cloud.

DvR

On DvR Controllers in a DvR domain, you must manually configure IP multicast over Fabric Connect on Layer 3 VSNs (VRFs). This configuration is then automatically pushed to the Leaf nodes in the DvR domain.

For more information on DvR, see Distributed Virtual Routing.