Design Reference

current release and identify two VLANs to use as B-VLANs. SPBM then automatically creates a
virtual backbone MAC for the IST pair, and advertises it with IS-IS. By operating two SPBM switches
in switch clustering (SMLT) mode, you can achieve redundant connectivity between the C-VLAN
domain and the SPBM infrastructure. This configuration allows the dual homing of any traditional
link aggregation capable device into an SPBM network.
SMLT with IP multicast over SPBM
Layer 2 access switches use IGMP Snooping to prune multicast traffic. In IP multicast over SPBM,
BEBs are the IGMP queriers, therefore access switches forward multicast data from the senders as
well as IGMP control messages from receivers to the BEBs.
1. When a sender transmits multicast data to the Layer 2 access switch that has an MLT to the
switch cluster, the multicast data is hashed towards one or the other BEBs in the switch
cluster.
2.
The receiving BEB allocates a Data I-SID and sends a TLV update on the primary B-VLAN,
to announce the availability of the stream to its neighbors.
3. The BEB propagates the TLV update through the SPBM fabric in an LSP, so all BEBs are
aware of this stream availability.
4. The sender information is also synchronized over the IST to the peer switch.
5. Then the peer switch allocates a Data I-SID for the multicast stream, and sends a TLV
update on the secondary B-VLAN to announce the stream availability.
Campus architecture
For migration purposes, you can add SPBM to an existing network that has SMLT configured. In
fact, if there are other protocols already running in the network, such as Open Shortest Path First
(OSPF), you can leave them in place too. SPBM uses IS-IS, and operates independently from other
protocols. However, Avaya recommends that you eventually eliminate SMLT in the core and
eliminate other unnecessary protocols. This reduces the complexity of the network and makes it
much simpler to maintain and troubleshoot.
Whether or not you configure SMLT in the core, the main point to remember is that SPBM separates
services from the infrastructure. For example, in a large campus, a user may need access to other
sites or data centers. With SPBM you can grant that access by associating the user to a specific I-
SID. With this mechanism, the user can work without getting access to confidential information of
another department.
The following figure depicts a topology where the BEBs in the edge and data center distribution
nodes are configured in SMLT clusters. Prior to implementing SPBM, the core nodes would also
have been configured as SMLT clusters. When migrating SPBM onto this network design, it is
important to note that you can deploy SPBM over the existing SMLT topology without network
interruption. After the SPBM infrastructure is in place, you can create VSN services over SPBM or
migrate them from the previous end-to-end SMLT-based design.
SPBM design guidelines
86 Network Design Reference for Avaya VSP 4000 Series January 2015
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