On some [older/ancient] BMCs, the BMC shares the same MAC address as the host interface.

# ifconfig eth0
eth0      Link encap:Ethernet  HWaddr 00:1F:C6:16:0A:91  
          inet addr:140.252.6.20  Bcast:140.252.6.255  Mask:255.255.255.0
          inet6 addr: fe80::21f:c6ff:fe16:a91/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:1071916861 errors:1 dropped:0 overruns:0 frame:1
          TX packets:210694687 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:1210304125909 (1.1 TiB)  TX bytes:178033703764 (165.8 GiB)
          Base address:0x2000 Memory:c8200000-c8220000 

# ipmitool lan print 
Set in Progress         : Set Complete
Auth Type Support       : NONE MD2 MD5 PASSWORD 
Auth Type Enable        : Callback : NONE MD2 MD5 PASSWORD 
                        : User     : NONE MD2 MD5 PASSWORD 
                        : Operator : NONE MD2 MD5 PASSWORD 
                        : Admin    : NONE MD2 MD5 PASSWORD 
                        : OEM      : NONE MD2 MD5 PASSWORD 
IP Address Source       : Static Address
IP Address              : 140.252.26.96
Subnet Mask             : 255.255.255.0
MAC Address             : 00:1f:c6:16:0a:91
SNMP Community String   : public
IP Header               : TTL=0x40 Flags=0x40 Precedence=0x00 TOS=0x10
BMC ARP Control         : ARP Responses Enabled, Gratuitous ARP Disabled
Gratituous ARP Intrvl   : 2.0 seconds
Default Gateway IP      : 140.252.26.1
Default Gateway MAC     : 00:30:48:41:93:28
Backup Gateway IP       : 0.0.0.0
Backup Gateway MAC      : 00:00:00:00:00:00
802.1q VLAN ID          : Disabled
RMCP+ Cipher Suites     : 0,1,2,6,7
Cipher Suite Priv Max   : aaaXXXaaXXXXXXX
                        :     X=Cipher Suite Unused
                        :     c=CALLBACK
                        :     u=USER
                        :     o=OPERATOR
                        :     a=ADMIN
                        :     O=OEM

In 1.1, you can not add a BMC interface to a host as foreman complains that the mac address is already in use. I'm not sure if this issue is even worth fixing as I've only see this on very old systems but it may be worth noting the existence of this limitation.