Brocade Network OS Administrator’s Guide v4.1.1 - Manual (Page 375)

Configuring Virtual Fabrics
● Virtual Fabrics overview................................................................................................ 375
● Configuring and managing Virtual Fabrics.................................................................... 397
Virtual Fabrics overview
The Virtual Fabrics feature delivers Layer 2 Multitenancy solutions that provide support for overlapping
VLANs, VLAN scaling, and transparent VLAN services by providing both traditional VLAN service and a
transport service. These services are offered by provisioning a Virtual Fabric (VF) in the data center. A
VF operates like a regular 802.1Q VLAN, but has a 24-bit address space that allows the number of
networks to scale beyond the standard 4K (4096) limit. The transport service is provided by configuring
a transport VF, whereas traditional Layer 2/Layer 3 VLAN service is provided by configuring a service
VF.
The Virtual Fabrics feature is deployed in data centers where logical switch partitioning and server
virtualization require a large number of customer VLAN domains that must be isolated from each other
in the data plane. On the hardware platforms that support this feature, the Brocade VDX 8770 series
and the Brocade VDX 6740 series running Network OS release 4.1.0 or later, the VLAN ID range is
extended from the standard 802.1Q limit of 4095, to extend through 8191 on both a local RBridge and in
a single VCS Fabric.
Data center virtualization, such as that provided by VMware vCenters, challenges network design in a
variety of areas. Large numbers of networks can be required to support the virtualization of server hosts
and multiple-tenant virtual machines (VMs), with Ports on Demand (POD) for the virtual data center
(vDC) leading to POD configurations replicated at different ports. Such virtualization topologies are
inherently largely independent of physical networks, with VM network configurations decoupled from the
addressing and configurations of physical networks. The underlying Layer 2/Layer 3 infrastructure is an
extension of a VMware virtual switch, or vSwitch, requiring address mapping at the boundary between
the physical and virtual networks. In addition, the requirement for VM mobility makes it necessary to
support the migration of VMs across the Virtual Cluster Switching (VCS) data center or across
geographically separated sites, independently of the connectivity of the underlying infrastructure.
When a fabric is VF-enabled, existing VLAN configurations can apply to any VLAN. When a fabric is not
VF-enabled, VLAN classification is not supported, and VLAN configurations are 802.1Q VLANs with
VLAN IDs 1 through 4095.
A Virtual Fabric is just like a regular 802.1Q VLAN, but with a 24-bit address space that has the
potential to support up to approximately16 million VLANs to be provisioned in the fabric. This VF VLAN
address space is common to regular 802.1Q VLANs and classified VLANs. VLAN IDs from 1 through
4095 identify a conventional 802.1Q VLAN. VLAN IDs greater than or equal to 4096, up through 8191,
identify VFs that need frame classification. A VF VLAN ID is unique within a local VCS Fabric, but may
not be unique across multiple VCS Fabrics.
NOTE
A service VF is defined on the basis of the encapsulation classification of the ingress frame, with frames
classified at the edge port according to the 802.1Q VLAN ID or MAC address. For the same service VF,
the 802.1Q classification rule at each interface is a link-local configuration; the rule may be different at
each interface.
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