When a switch boots up or joins a new fabric, it can request a specific domain ID (statically configured) or take any available domain ID.
The Fibre Channel domain (fcdomain) feature performs principal switch selection, domain ID distribution, FC ID allocation, and fabric reconfiguration functions as described in the FC-SW-2 standards. The domains are configured on a per-VSAN basis. If you do not configure a domain ID, the local switch uses a random ID.
This section describes each fcdomain phase:
- Principal switch selection —This phase guarantees the selection of a unique principal switch across the fabric.
- Domain ID distribution —This phase guarantees each switch in the fabric obtains a unique domain ID.
- FC ID allocation —This phase guarantees a unique FC ID assignment to each device attached to the corresponding switch in the fabric.
- Fabric reconfiguration —This phase guarantees a resynchronization of all switches in the fabric to ensure they simultaneously restart a new principal switch selection phase.
By default, the Fibre Channel domain feature is enabled on each switch. If you disable the Fibre Channel domain feature in a switch, that switch can no longer participate with other switches in the fabric.
If the configured domain ID is
static, the switch requests a particular domain ID. If it does not get that domain ID, the assigned domain ID is discarded. All local interfaces are isolated, and the local switch assigns itself the configured domain ID, which becomes the runtime domain ID.
If the configured domain ID is
preferred, the local switch accepts the domain ID assigned by the principal switch and the assigned domain ID becomes the runtime domain ID.
To configure a switch with a preferred or static domain ID, use the following steps :
switch # configure terminal
switch (config) # fcdomain domain domain-id [preferred | static] vsan vsan-id
Fibre Channel domains can be started disruptively or non-disruptively.
If you perform a disruptive restart, reconfigure fabric (RCF) frames are sent to other switches in the fabric, and data traffic is disrupted on all the switches in the VSAN (including remotely segmented ISLs).
If you perform a non-disruptive restart, build fabric (BF) frames are sent to other switches in the fabric, and data traffic is disrupted only on the switch whose configured domain is static and numerically not the same as its runtime domain (for example, the configured domain is 11 static and the runtime domain is 99).
To restart the fabric non-disruptively in VSAN, use the following configuration steps:
switch # configure terminal
switch (config) # fcdomain restart vsan vsan-id
To restart the fabric disruptively, use the
fcdomain restart disruptive vsan vsan-id command. Irrespective of how many switches in that VSAN are configured, this command will cause all devices of all switches in that VSAN to log out, causing data traffic disruption.