Brocade Network OS Administrator’s Guide v4.1.1 - Manual (Page 379)

NOTE
If the fabric state is VF-incapable, the vcs virtual-fabric enable command will not succeed.
Disabling VFs
To disable VFs in the fabric, the user must first remove all VF configurations in the fabric before issuing
the no vcs virtual-fabric enable command. This command is distributed to all RBridges in the fabric.
Each RBridge reverses the stage execution from what was done to enable the VF. When ISL
encapsulation returns to being C-TAG based, the fabric is in a VF-capable state.
NOTE
Prior to issuing the no vcs virtual-fabric enable command, the user must ensure that all new
commands and enhanced commands that reference VFs (VFs with IDs greater than 4095) in the fabric
are removed from the running configuration. Otherwise, the command will be rejected.
Joining a switch to the fabric
If VFs are disabled in the startup-config, the RBridge will not able to join a VF-enabled fabric upon
reboot. Although the RBridge may form ISLs with a neighbor RBridge at the link level, the RBridge will
be segmented from the VF-enabled cluster because of a capability mismatch.
In order for the RBridge to join a VF-enabled cluster, the procedures described in Upgrading and
downgrading firmware with Virtual Fabrics on page 404 must apply to the segmented RBridge. At the
end of the procedures, the segmented RBridge will also be in the VF-enabled state. All segmented ISLs
on the RBridge are automatically toggled so that it can rejoin the fabric.
Default Virtual Fabrics state
A switch after a netinstall is VF-incapable in the default configuration. It will fail to join a VF-enabled
cluster when it reboots.
The default VF state in the startup configuration is changed when the copy default-config startup-
config command is executed. The resulting state is the same as the current VF state of the fabric.
Virtual Fabrics configuration overview
This section addresses a variety of Virtual Fabrics architecture scenarios and configuration issues
related to service VFs.
Virtual Fabrics performance considerations
VLAN configurations, whether for 802.1Q or classified VLANs, are VCS Fabric global configurations that
are distributed to all RBridges in the fabric. If there are 100K VLANs in the data center, this implies that
as RBridge will receive all those configuration, even though the RBridge could support a maximum of
8K (8192) VLANs. The processing of VLAN configurations for classified VLANs that are not actually
provisioned in the RBridge introduces performance overhead. The impact of this will be manifest in
configuration playback during system boot up and will result in a longer time for the fabric to reach a
ready state to forward data.
Virtual Fabrics configuration overview
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