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Ethernet Switches & Routers

New Contributor
Posts: 4
Registered: ‎01-06-2011

Spanning Tree on a stack hooked together in a loop

I have a stack of four FCX 648s.  The switches are hooked together in a ring topology using the CX4 interconnect.  Now since it is a loop would you need to run a STP protocol like your Fast Port on the switch?  I wonder as the active controller manages the whole stack and it uses a single MAC address so it would seem that you don't need to run a STP protocol.

So if I say no spanning on the switch am I in trouble?  These switches are edge devices connecting ro compute nodes in a cluster.

Also it seems that setting hittless failover and setting the mac address for the stack to what the active controller is necessary for failback and also to stay away from a spanning tree issue.  Is that correct?

Do you have a "best practice manual on these switches and how to manage them in a stack?

Frequent Contributor
Posts: 117
Registered: ‎07-26-2010

Re: Spanning Tree on a stack hooked together in a loop


Please check the following doc here in the communities:

Hitless FCX stacking best practise.

If you use the dedicated stacking ports on a FCX-6xxS then a special stacking protcol is managing the stack and the "loop". It is not the common STP which you configure on the FCX.

Hope this helps,


Posts: 56
Registered: ‎08-22-2008

Re: Spanning Tree on a stack hooked together in a loop

Would you not use RSTP as this is faster, if it supports it. If they are in a ring / loop using the correct part you may not need to do anything, On the HP units I have fitted using their casscade module it sets it up for you, then if you happen to add another interconnect in to your stack it will change to blocking,

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