Network Virtualization using Extreme Fabric Connect

Network Virtualization Using Extreme Fabric Connect
© 2019 Extreme Networks, Inc. All rights reserved. 41
Customer MAC Address
A Customer MAC address (CMAC) is a MAC address that belongs to an end station, server/VM or in general
any device that is not running SPB. CMACs only exist within Fabric Connect VSN services and are never
seen or used within the SPB Backbone VLANs.
Backbone MAC Address
A Backbone MAC address (BMAC) is a MAC address that belongs to an SPB node in the Ethernet Fabric
and only exists inside the SPB fabric (as opposed to end-station user-MAC addresses, which only exist
inside user-VLANs or L2 VSNs). In the Mac-in-Mac encapsulation, the outer Ethernet header will contain a
Destination BMAC (which determines the egress SPB node, or service-specific multicast tree, across the
Fabric for the packet) and a Source BMAC (which indicates which BEB added the Mac-in-Mac
encapsulation to the packet when it entered the fabric). Every SPB node allocates one (or more) BMACs
and IS-IS announces these BMACs to every other node in the Ethernet fabric so that all nodes can compute
the shortest path towards each BMAC in the fabric.
Tip
There are not that many BMACs in an SPB fabric. In the Extreme Networks implementation
SPB nodes allocate these BMACs:
• One BMAC for every BEB or BCB node (same as IS-IS System ID).
• One SMLT-Virtual-BMAC shared across both BEBs forming an SMLT cluster.
• One BMAC for the encapsulation of SPB IP Multicast traffic on nodes acting as
ingress BEBs for the IP Multicast streams.
Note that with SPB, one of the node’s BMAC addresses (the unique globally assigned one) is also the node’s
IS-IS System ID and in fact is configured as such.
Note
It usually makes sense to configure the IS-IS System ID / node BMAC into an easily
recognizable format, such as Locally Administered Address, or LAA. For example,
02yy.yyxx. xxss
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where the yy.yy bytes can reflect the location of the node in the SPB
network while ensuring that xx.xx remains a fully unique number across the SPB network,
which can then also be reused to generate a unique SPBM nick-name and ss is used for the
SMLT Virtual-BMAC. Alternatively, the burnt in MAC address will be used to derive it.
SMLT-Virtual-BMAC
When two BEB nodes are combined into a Multi-chassis Link Aggregation Group (MLAG), this is done via
configuration of Extreme’s SMLT clustering, which requires an IST or Virtual-IST (vIST) connection between
the two BEBs. This will be further covered in a later section.
The two BEBs forming the SMLT cluster operate as one logical L2 BEB in that they can share SMLT
connections and share and synchronize their respective L2 VSN MAC tables. To be seen as one single
logical BEB by the rest of the SPB fabric, the SMLT cluster will allocate a unique SMLT-Virtual-BMAC that
will be used by both BEBs as source BMAC, instead of the nodal BMAC, to encapsulate any CVLAN traffic
received from local UNI ports and Mac-in-Mac encapsulated to cross the SPB fabric. When this traffic is
received by distant egress BEBs, reverse MAC learning will ensure that those distant BEBs will associate the
source CMACs with the SMLT-Virtual-BMAC of the SMLT cluster where those CMACs are located. This will
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For guidelines on allocating SPB unique identifiers refer to reference documentation [8].
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