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I stacked two 3750G Cisco switches a few weeks ago, all go. But, yesterday I installed a 2nd stacking cable as well for full optimization. However, it is not registering it seems.

Cisco3750#sh switch stack-ports
  Switch #    Port 1       Port 2 
  --------    ------       ------ 
    1           Ok          Down  
    2           Ok          Down 

I did a little Googling, found these two. Is this the correct way to enable the 2nd stacking cable?

switch 1 stack port 2 enable
switch 2 stack port 2 enable

EDIT 4PM: Another search says to cross the cables (crisscross). Not sure what's up here, but the above commands to enable did not cut it.

Each 3750 switch’s back has two stack ports 1 and 2.

Suppose you want to connect two switches with two stack cables:

1st switch port 1 connects to 2nd switch port 2.

1st switch port 2 connects to 1st switch port 1.

The stack cables will be crossed.

UPDATE #2 10:30PM

Powered off, looped stacking cables as suggested, powered on. Shows the loop (port 1 to port 2, vice versa) but 2nd cable still not registering.

Cisco3750#switch 1 stack port 2 enable
Enabling/disabling a stack port may cause undesired stack changes. Continue?[confirm]
Cisco3750#switch 2 stack port 2 enable
Enabling/disabling a stack port may cause undesired stack changes. Continue?[confirm]

Cisco3750#show switch stack-ring speed

Stack Ring Speed        : 16G
Stack Ring Configuration: Half
Stack Ring Protocol     : StackWise

Cisco3750#sh switch stack-ports       
  Switch #    Port 1       Port 2 
  --------    ------       ------ 
    1           Ok          Down  
    2          Down          Ok 
  • 1
    I'd suggest trying it. Why are you asking here if you haven't already? – ewwhite Jan 4 '16 at 14:38
  • Why? Because I'm asking if it's the correct way, that's why I'm asking. – Cazzette Jan 4 '16 at 17:56
  • You do that to create a loop. When you stack more than two switches, it is important to do that so that any single cable loss doesn't isolate switches. With a loop, the loss of a single link still leaves all switches connected. – Ron Maupin Jan 4 '16 at 21:57
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When you have a stack of switches, you want to create a loop with the stacking cables. Port 2 on one switch connects to port 1 on the next switch. Continue that until the last switch which will connect back to the first switch.

This creates a loop in the switch connections. When you lose one link in the loop, you will still have a continuous link between all the switches. Without a loop, you will end up with two groups of switches isolated from each other.

This is a picture of how you should connect. It is for 3750X switches, but the stacking principle is the same for all the stacking switches.

enter image description here

  • Thanks @Ron Maupin. So this applies even if the stack is just 2 switches? If I do this, I assume my output will show both ports on and full 32G? – Cazzette Jan 5 '16 at 2:19
  • You don't double the bandwidth, you gain redundancy. Since each switch comes with a StackWise cable, you get it for free. If you have more than three switches, and you use horizontal cable management (recommended), you will probably need to get one of the longer cables. – Ron Maupin Jan 5 '16 at 2:28
  • Ok confused. Right now they're stacked 2 switches, 16G stack ring speed and half stack ring config. I was told a 2nd cable would make it a full 32G? imgur.com/a1ygvSP @RonMaupin – Cazzette Jan 5 '16 at 2:34
  • 1
    Not that I have heard of. Cisco has a paper about the StackWise technology Cisco StackWise and StackWise Plus Technology. – Ron Maupin Jan 5 '16 at 2:37
  • thank you. It does say 32G but I'll give it a shot and see. – Cazzette Jan 5 '16 at 2:42

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