When running Switch Engine, each universal hardware switch uses a base MAC address at offset 0 for both the default management port, if available, and in-band VLAN utilizing DHCP, for example, 00:c0:cc:8b:68:00. When the switch runs Fabric Engine, it uses a base MAC at offset 0x81 for the default management port (for example, 00:c0:cc:8b:68:81) and offset 256 for the in-band VLAN (for example, 00:c0:cc:8b:69:00).
Note
The address assignment for the in-band VLAN assumes that the VLAN has a mac-offset value of 0 assigned. If a different mac-offset value is assigned, the MAC address changes accordingly. For example, if mac-offset is 10, then the associated MAC address is 00:c0:cc:8b:69:0A.When using a DHCP client on the switch, the switch sends a common DHCP client identifier equal to the base MAC address of the switch that is printed on the switch label. Because of this, assuming a standard DHCP pool configuration, the DHCP server always recognizes the switch by the same IP address, regardless of whether Switch Engine or Fabric Engine runs on the switch.
To statically assign IP addresses on the DHCP server, assign them based upon the DHCP client ID. This assignment will ensure that the bindings do not change when the switch alternates between Switch Engine and Fabric Engine. If you assign the DHCP IP addresses based on MAC addresses, configure multiple entries, one for the 0 offset and one for the 0x81 offset, to account for the different ways in which the two operating systems assign base MAC addresses.