User guide
HP Virtual Connect for Cisco Network Administrators (version 4.x)
Document Number: C01386629 Date: January 2014
page 40
complexity of troubleshooting network related issues.
•
Server application licensing is maintained after hardware changes
Many server application licensing mechanisms can key off the server’s MAC addresses.
If the server’s MAC address changes (replacing a failed NIC, booting server image on a
different physical server, etc.), then the application licensing may require re-licensing
using the new MAC address. Virtualized MAC addresses do not prevent this problem.
However, VC’s use of managed MAC addresses does prevent this problem since the
server image will always see the VC managed MAC address regardless of which physical
server it is running
on.
•
No Performance impact on network devices
Virtualized MAC addresses can require that a network device (e.g. switch) manipulate
every frame a server transmits to replace the server’s MAC address with the
virtualized
MAC address. Also, when the source MAC address is edited by the network device, the
frames checksum (CRC) has to be recomputed by the network device. The more frames a
server transmits, the more work the network device has to do, which can have an
impact on the performance of the network device. Alternatively, VC’s use of managed
MAC addresses means the server transmits with the managed MAC address. No device
on the network (VC or switch) is required to manipulate the server’s frames. This results
in absolutely no performance impact on the network.
When a blade server with VC managed MAC addresses is removed from the enclosure (or when a
VC Server Profile is unassigned from a server blade while still in the enclosure) the blade
server automatically reverts back to the actual MAC addresses burned into the physical NICs
at the factory. This prevents any issues with duplicate MAC addresses on the network caused by
moving blade servers around within the data center.
Virtual Connect Manager (VCM) provides three domain-wide choices for managing the blade
server MAC addresses:
•
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.