HP Virtual Connect 8Gb 24-port Fibre Channel Module for c-Class BladeSystem - Manual (Page 147)

Configuring the Virtual Connect domain using the CLI 147
individual network in the Virtual Connect environment, VC blocks certain stacking links to ensure that
each network has a loop-free topology.
The loop avoidance feature cannot be disabled or changed. However, the preferred uplink connection for a
network can be identified when defining network uplinks.
VCM loop avoidance does not extend to server downlink ports. If a loop is formed on the server downlink
ports, any BPDUs traversing the VC domain from an uplink through server downlinks is transmitted back to
the uplink port on the external switch. If this external switch is enabled for BPDU loop protection, the uplink
port is disabled, causing network disruption. VCM has a network loop protection feature that provides the
ability to intercept the BPDU packets on the server downlink ports and disable the server downlink port to
prevent a loop condition. You are notified of this condition and can take action to reset the server downlink
ports.
VCM provides the ability to enable or disable network loop protection. The feature is enabled by default and
applies to all VC-Enet modules in the domain.
A reset command resets and restarts network loop protection for all server ports in a “loop-detected” error
condition.
Server blade power on and power off guidelines
Certain server profile changes require the server blade in the device bay to be powered off before the
change can be made. HP recommends that administrators power off servers with the server console before
attempting such operations within the Virtual Connect Manager.
If any changes are made to a server profile that require modifications to the server, the server blade must be
powered off. Network or fabric changes do not require the server blade to be powered off. Server side
settings include the following:
• Assigning a VC- or user-defined MAC address
• Changing the PXE setting
• Assigning a VC-defined WWN
• Changing the Fibre Channel boot parameters
• Changing iSCSI boot parameters
• Adding or deleting a connection of any kind
If any of the listed settings are changing, the server must be powered off before the profile action can occur.
If the server blade is not powered off, a message appears and no changes are made. In this case, power off
the server blade and repeat the action.
When server side settings are changing, the following operations require that server blades be powered off:
• Assigning a profile to a server blade already installed in a device bay
• Deleting a profile, moving a profile to a different device bay, or unassigning a profile from the existing
bay
• Making modifications to a profile that affect settings on the server blade; for example, PXE
enable/disable, changing the number of connections, or changing Fibre Channel boot parameters
• Assigning a VC-assigned serial number
The following operations do not require the server blade to be powered off:
• Changing the network connected to an already defined Ethernet port