Cisco 3750 Stack, few basic questions

nikhil.kulkarni · ‎12-22-2014

Hi,

I was going through some videos on the Architecture of the Cisco stack architecture and the working.

Few questions:

I wanted to know if the stack ring also runs some kind of spanning tree within itself to block potential loops. If yes, any command to check the working?
If I have a topology of 3 switches with switch A connected to switch B and then switch B connected to switch C, what is the only advantage that I get if I connect switch C back to switch A? I mean is there any bandwidth or speed advantage that can be achieved?

Thanks,

Nik

Reza Sharifi · ‎12-22-2014

Hi,

I wanted to know if the stack ring also runs some kind of spanning tree within itself to block potential loops. If yes, any command to check the working?

No, there is no spanning tree involved. The stacking cable makes the entire stack as one switch.

If I have a topology of 3 switches with switch A connected to switch B and then switch B connected to switch C, what is the only advantage that I get if I connect switch C back to switch A? I mean is there any bandwidth or speed advantage that can be achieved?

Yes, you want to use 2 stacking cables per switch to get the full bandwidth. So, 1 to 2, 2 to 3 and 3 to 1 (ring) depending on the switch, it will give you 16 or 32Gig of back plane.

HTH

Leo Laohoo · ‎12-22-2014

If I have a topology of 3 switches with switch A connected to switch B and then switch B connected to switch C, what is the only advantage that I get if I connect switch C back to switch A? I mean is there any bandwidth or speed advantage that can be achieved?

If you don't connect "C" back to "A" then you loose redundancy. If you loose "B" then you will have a "split brain" scenario.

Another benefit of connecting "C" back to "A" is the stack-ring speed. If you form a loop your speed is 32- (Stackwise) or 64 Gbps (Stackwise Plus) full dupex. If there is no close loop then the speed is 32- or 64 Gbps HALF duplex.

Have a read of this document: Cisco StackWise and StackWise Plus Technology