I got two CISCO switches of same model. (they're connected for trunking and spanning-tree is enabled (by default)) – I tried to leave the configuration as default as possible.
I got a server with two NICs, NIC teaming is configured.
Each NIC is connected to each switch. (the NIC teaming app sets up a random MAC address and is using it for both NICs instead of their factory assigned MACs)
Switches complains about MAC address flapping.. But why? Isn't the switch smart enough to know that my server have fault tolerence and is using two network cables? What configuration am I missing?
EDIT: The actually question is highlighted.. The rest is just ranting.. hehe
Best Answer
Unless your switches are Cisco VSS capable (typically the high-end boxes) then you have to switch the NIC teaming to working in an active/passive mode rather than active/active.
The reason is that as it stands both switches have their own, completely separate, CAM table, but your team announces the same MAC down each physical port, in this case to different switches unaware of the team - so ST/portfast just flaps which switch owns the MAC address.
As I said if you had VSS switches they share one CAM table so you can split a team like this, that's what it's for in fact - but not for regular non-VSS switches sorry.