Multiple-Active Detection (MAD) is used to detect a split brain in an IRF system. When the MAD BFD method is used, a dedicated Layer3 VLAN interface needs to be configured for the MAD BFD operation.
This VLAN should be directly connected through an interface on each IRF member. Transit Layer2 device are supported, you just need to ensure they do not perform any kind of Layer2 blocking (STP or the like) on these ports.
This also means that the IRF member switches must offer a physical interface for the MAD BFD operation.
On the 6125XLG R2406P02, a new feature has been released which now supports the configuration of the MAD BFD on the Management Ethernet interface. This means that the MAD BFD can use the basic OOB Management Ethernet port, instead of taking an expensive 10G interface on the switch.
We’ll see if this becomes available on the other Comware7 switches as well.
1/ I have not been able to test this yet, so it is unclear for me if the MAD BFD IP can co-exist with a normal IP address for OOB Management on the same interface.
2/ I have also not tested if this update also included support for a VRF for the MAD BFD processing, I will try this in an upcoming test as well.
UPDATE 13/02/2015: I was able to test the feature and based on the test it seems:
* Management IP can co-exist with the MAD BFD IP address configuration on the M-G0/0/0 interface. When split-brain occurs, the M-G0/0/0 is by default shutdown by the MAD process on the slave side.
WARNING: When the M-G0/0/0 is excluded from mad (mad excluded interface configuration), both IRF sides keep the M-G0/0/0 interface UP, which results in an IP address conflict for the main interface. So I would recommend to keep the default, which means the M-G0/0/0 on the slave side will be shutdown by MAD.
* No VRF support: MAD BFD does not seem to work when an IP vpn-instance is configured on the Management interface. So it only worked when no management VRF was used.