Here's the MAC before the machine reconfiguration. We're doing DHCP reservations and while the machine is being reconfigured and firmware being updated I go and change the dhcp reservation. It seems though that vmk0 is holding onto the MAC address even after the boot.
The host profile which was previously applied has a setting of "Prompt the user for the MAC address if no default is available" for the management interface.
C:\Users\xxxx>
C:\Users\xxxx> $esxhost = get-vmhost xxxxxxxxxx
C:\Users\xxxx> $mgmt = $esxhost | Get-VMHostNetworkAdapter | ? { $_.Name -eq "vmk0" }
C:\Users\xxxx> $mgmt
Name Mac DhcpEnabled IP SubnetMask DeviceName
---- --- ----------- -- ---------- ----------
vmk0 xx:xx:xx:xx:00:5a True xxx.xxx.xxx.141 255.255.255.0 vmk0
Machine Reconfig done within UCS (Firmware update and vnic changes)
C:\Users\xxxx> $mgmt = $vmhost | Get-VMHostNetworkAdapter | ? { $_.Name -eq "vmk0" }
C:\Users\xxxx> $mgmt
Name Mac DhcpEnabled IP SubnetMask DeviceName
--- --- ----------- -- ---------- ----------
vmk0 xx:xx:xx:xx:00:5a True xxx.xxx.xxx.24 255.255.255.0 vmk0
C:\Users\xxxx> Get-UcsServiceProfile xxxxxxxxxx| Get-UcsVnic | select name,addr
Name Addr
---- ----
esx-vmnic0-mgmt xx:xx:xx:xx:00:4B