Multi-area SPB

Table 1. Multi-area SPB product support
Feature	Product	Release introduced
Multi-area SPB Boundary Node	5320 Series	Not Supported
	5420 Series	Not Supported
	5520 Series	Fabric Engine 8.10
	5720 Series	Fabric Engine 8.10
	7520 Series	Fabric Engine 8.10
	7720 Series	Fabric Engine 8.10
	VSP 4900 Series	Not Supported
	VSP 7400 Series	VOSS 8.4
Static data I-SID redistribution for Multi-area SPB Boundary Node	5320 Series	Not Supported
	5420 Series	Not Supported
	5520 Series	Fabric Engine 8.10
	5720 Series	Fabric Engine 8.10
	7520 Series	Fabric Engine 8.10
	7720 Series	Fabric Engine 8.10
	VSP 4900 Series	Not Supported
	VSP 7400 Series	VOSS 8.8
Virtual NNI links for Multi-area SPB Boundary Nodes	5320 Series	Not Supported
	5420 Series	Not Supported
	5520 Series	Not Supported
	5720 Series	Fabric Engine 9.1
	7520 Series	Fabric Engine 9.0.3
	7720 Series	Fabric Engine 9.0.3
	VSP 4900 Series	Not Supported
	VSP 7400 Series	VOSS 9.0.3

The Multi-area SPB feature enables building a scalable Shortest Path Bridging (SPB) network, consisting of multiple Intermediate System-to-Intermediate System (IS-IS) areas that connect to each other through the boundary nodes. The Multi-area SPB feature provides flexible network design through which you can group the nodes in the areas on a need basis.

Each area in the Multi-area SPB network contains the interior nodes and the boundary nodes.

Tip

As a best practice, ensure you have a high-speed direct physical connection between boundary nodes.

Each boundary node runs two Intermediate-System-to-Intermediate-System (IS-IS) instances, representing the home area and the remote area. Each IS-IS instance runs the Shortest Path First (SFP) computation and uses its own Link State Database (LSDB). The boundary nodes support Backbone Edge Bridge (BEB) functionality in addition to the Backbone Control Bridge (BCB) configuration and the UNIs belong only to the home area. You can configure IS-IS interfaces on each instance.

Note

The boundary nodes do not support Auto-sense for remote interfaces. You must manually configure all remote NNI on the boundary nodes. Each time the port receives a Fabric Connect TLV, the port is configured as NNI in the home area. You must disable Auto-sense on the IS-IS remote area ports.

The multiple areas in the Multi-area SPB network connect in various patterns, for example, the hub and spoke topology and the daisy chain topology.

Designated and Non-designated Boundary Nodes

Among the boundary nodes in the Multi-area SPB network, the system elects the designated boundary node on basis of the unique chassis MAC value of the node. The nodes in the SPB area advertise their chassis MAC value using the link state packet (LSP) and the system elects the node with the smallest chassis MAC value as the designated boundary node.

The functions of the boundary nodes in the Multi-area SPB network are:

Designated boundary node:
- Creates the area virtual node LSPs on each IS-IS instance.
- Configures the virtual node's adjacency with the other boundary node on basis of the reachability of the node.
- Advertises the services on the area virtual node on basis of the redistribution policies that you configure.
Non-designated boundary node:
- Connects to the area virtual node and the system uses it to forward the traffic on basis of the IS-IS computation.
- Takes over as the designated boundary node if the designated boundary node is no longer available in any area.

For more information about the area virtual node, see Area Virtual Node.

Minimum Requirements

The minimum requirements for the Multi-area SPB to function are:

Two boundary nodes to provide redundancy.
Multi-area SPB redistribution policies between areas, like Layer 2 redistribution, Layer 3 unicast redistribution, multicast redistribution, Distributed Virtual Routing (DvR) backbone redistribution and so on. For more information, see Multi-area SPB Redistribution and Policies.