The following list identifies the restrictions and considerations that apply to the Multi-area SPB feature:
The maximum number of nodes that can perform the functionality of boundary node between any given pair of areas is two. The two boundary nodes can be either in a vIST configuration (paired with each other) or in a non-vIST configuration. Any other combination of two boundary nodes is not supported.
You must not connect the same Protocol Independent Multicast (PIM) domain to the SPB-PIM Gateway nodes that are in different Intermediate-System-to-Intermediate-System (IS-IS) areas, to avoid the inter-area redistribution of the same multicast information.
You can enable the Dynamic Nickname server on the boundary nodes in the home area, but the boundary nodes cannot be clients in any of the two areas. The boundary nodes do not support the Dynamic Nickname server in the remote area.
You must manually configure the backbone VLANs (B-VLAN) on the boundary nodes, so the system does not learn the dynamic values that it receives through the Link Layer Discovery Protocol (LLDP). However, the system sends the manually configured B-VLANs on the BN through LLDP, so that other neighbors can learn them (both in home and remote areas).
If you enable Auto-sense on a port connected to remote area node and the port receives a Fabric Connect TLV through LLDP then the port transitions to the NNI pending state and the system logs a message. In this state, the system does not enable IS-IS remote area, and no IS-IS adjacency forms. For more information, see Auto-sense Port States.
If the system forms an adjacency between two boundary nodes that are part of the home and remote area, the hello packets in the home area will use the home manual area and the hello packets in the remote area use the remote manual area.
If the system forms a home and a remote adjacency on the same port then the Multi-area SPB feature uses different Backbone VLAN IDs (B-VIDs) for each adjacency, the home adjacency uses the primary B-VID and the remote adjacency uses the secondary B-VID.
If the system forms an IS-IS adjacency in both the home and remote areas on a boundary node, of the same port then the remote adjacency stays up only with another boundary node that also has IS-IS configured on both the home and remote areas of the same port.
If a boundary node connects to a Backbone Edge Bridge (BEB) in the remote area and if you configure IS-IS in the home area on the same interface, then the remote adjacency goes down.
On the boundary node, to install a route from a remote area in the routing table manager (RTM), the route must pass the accept policy and the Multi-area SPB redistribution policy that you configure on the specific Virtual Router Forwarding (VRF) instance.
On the boundary node, to install an inter-VRF route from a remote area in the routing table manager (RTM), the inter-VRF route must pass the accept policy and the Multi-area SPB redistribution policy that you configure on both the source and destination VRF instances.
Nickname and system ID for the physical node and virtual node must be different.
When enabling Remote IS-IS Instance, make sure that the physical node nickname, virtual node nickname and system ID are different.