Failover with sticky MAC address on network switch

Question

Introduction:

I am configuring a server to have two ethernet ports (one as primary, the other is redundant) connected to two different switches. In the switches, I enabled the sticky MAC address and configured the two ports on the server as Net Switch Team and fixed a MAC address for the team.

the issue:

when doing the failover test, I unplugged the primary and the redundant link was up (as expected) but when I unplug the redundant before restoring the primary then restoring both links the server will not be able to ping the switch unless I turn off the Sticky MAC address off in the switches.

Note:

I am thinking maybe because the Ethernet Adapter Card has both ports in it and if I applied the same thing on two different ports in two different Ethernet adapter cards it will work fine. Is that true? and if yes why?

Thanks in advanced, Best regards.

Answer 1

Sticky MAC doesn't work because you're programming the network to have that MAC in a specific place (port). A MAC can only be in one place in the network. If that port is physically up, that's always where the traffic will go. When a MAC is pinned to two places -- on different switches, traffic on each of those switches will always flow to the local port, because that's how you've programmed it: Sticky MAC permanently populates the CAM table. A third switch will see that MAC bouncing from switch to switch depending on where it sees traffic. [In Cisco terms a "MAC FLAP"] With a MAC pinned to more than one place, you're relying on the redundant port(s) to be physically down, so the MAC is removed from the CAM table; when they aren't traffic doesn't go where it must.

Answer 2

It isn't entirely clear how the host fails over but the basic approach for active/passive is don't configure anything on the switch.

Instead, the host just needs to transmit a single frame with the redundant MAC address as source (physical or virtual), so the switch moves that MAC to the currently active port on failover or recovery. Making a MAC sticky on a certain port may prevent that mechanism from working, depending on the overall configuration.