Specifications

HP Virtual Connect for Cisco Network Administrators (version 1.2x) page 38
• Static, factory-default MAC addresses
As the name suggests, this setting tells Virtual Connect to not manage the server MAC
addresses. The server will only use the original factory burned-in MAC address.
• User-defined
This setting allows the Administrator to define a Locally Administered MAC address range
that Virtual Connect will use to assign to blade servers.
• HP Pre-defined (recommended)
This setting tells Virtual Connect to assign server MAC addresses from the pool of MAC
addresses that HP has reserved. This option allows the Administrator to choose from one
of 64 ranges of 1024 MAC addresses.
In addition, when using either the User-defined or HP Pre-defined settings as the domain-wide
default setting, each individual VC Server Profile can optionally override the domain-wide setting by
selecting to use the factory-default MAC address instead.
Important points about VC managed MAC addresses:
• VC only manages the MAC address of physical NIC ports on a blade server. VC does
not manage the MAC address used by virtual servers that may run on a physical server.
• A server reverts to the factory-default MAC address when removed from the enclosure or
when no VC Server Profile is applied to it.
• VC generates 2 MAC addresses per NIC port in order to support multi-function adapters
that may require more than one MAC address per port.
• Customers requiring a centralized database for managing the VC managed MAC
address pools should consider implementing Virtual Connect Enterprise Manager. See
www.hp.com/go/vcem for more details.
Spanning Tree
Since Virtual Connect does not present itself to the external Cisco network as another “Ethernet
switch”, the subject of “spanning tree interoperability” is not an applicable topic when discussing
the two products. In other words, in the same way that a server (with multiple NICs) does not need
to be configured for spanning tree, Virtual Connect (with multiple uplinks that look like NICs to the
external Cisco network) does not need to be configured for spanning tree either. This means that
the network administrator does not have to worry about STP interoperability issues between VC and
Cisco since VC uplink ports do not transmit or receive STP BPDUs (Spanning Tree configuration
frames) and cannot interfere with the external switched infrastructure’s implementation of STP any
more than a multihomed server can. This also means that all questions about PVST+ support, Rapid
Spanning Tree, MST, etc. are not applicable for Virtual Connect deployment discussions.
Since VC uplink ports simply look to the network like “regular old server ports” with multiple MAC
addresses, HP recommends that Cisco downlink ports connected to the VC uplink ports be
configured as if they are connected directly to server NIC ports. In other words, configure the Cisco
downlink ports as “access” or “trunk” ports with PortFast enabled. Enabling BPDUGuard is also an
acceptable option for customers that regularly enable it for other Cisco switch ports connected
directly to server ports. In summary, since Virtual Connect allows the c-Class enclosure to connect
to the external network in much the same way as a VMware ESX server connects to the external
network, it is easy to understand why Virtual Connect, just like a VMware ESX server, does not
participate in the external network’s spanning tree domain.