Brocade Network OS Administrator’s Guide v4.1.1 - Manual (Page 377)

STP support
The correct configuration of xSTP is the responsibility of the user. Much as the user must ensure that
VLAN configurations and VLAN instance mappings are consistent on all switch ports, so also the user
must understand whether a specific protocol, whether RSTP, MSTP, or PVST, is applicable to the
underlying physical topology when 802.1Q VLANs and VFs coexist in the fabric.
Brocade VDX 6740 series limitations
The Brocade VDX 6740 series platforms do not support full port-based C-TAG translation. Whenever
there is a translation conflict among the ports because the same C-TAG is used for different VLANs, the
conflict cannot be resolved without incurring severe internal VLAN ID (IVID) scalability constraints.
Optimal scalability is possible only when overlapping C-TAG classification occurs across port groups.
In a pure service VF deployment, these platforms support up to 4096 802.1Q VLANs and 2048
classified VLANs, assuming that each VLAN configured on a single port constitutes a single conflict.
In a pure transport VF deployment, these platforms support port-based transport VFs on every edge
port, and a total of 2048 combined 802.1Q and classified VLANs, assuming that each VLAN is
configured on a single port.
VCS extension and vCenter orchestration
Network OS 4.1.0 does not support the use of VFs to extend a VCS fabric to another VCS fabric, or to
orchestrate multiple vCenters.
High-availability considerations
In-Service Software Upgrade (ISSU) and high availability (HA) are supported for this feature on the
Brocade VDX 8770 series, but not on the Brocade 6740 series.
Virtual Fabrics upgrade and downgrade considerations
The following Virtual Fabric upgrade and downgrade considerations need to be kept in mind.
Virtual Fabrics backward compatibility
In Network OS release 4.1.0, the Virtual Fabrics feature is capable of support both regular 802.1Q and
VF configurations. RBridges that upgrade to Network OS 4.1.0 will continue to support 802.1Q
configurations that exist in the fabric.
Virtual Fabrics forward compatibility
The Virtual Fabrics feature is supported on Brocade VDX 6740 series, and VDX 8770 series platforms
beginning with Network OS 4.1.0. However, whether VF configuration is permitted on these platforms is
a global fabric-wide decision, and is not a platform-based decision. VF configuration is permitted only
when a fabric consists of VF-capable RBridges running in logical chassis cluster mode.
In earlier releases, every 802.1Q VLAN had to be configured on every RBridge. This configuration had
to be applied to every RBridge, even when that RBridge serves as a transit and did not terminate the
VLAN. This is because the RBridge only forwarded frames on an Inter-Switch Link (ISL) that were
associated with a configured VLAN. Beginning with Network OS 4.1.0, this restriction does not apply. In
logical chassis cluster mode, VLAN configurations are automatically distributed to all nodes; the user
does not have to configure VLANs on transit RBridges. A transit RBridge can always forward VLAN
Virtual Fabrics upgrade and downgrade considerations
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