Hot swap stacking cables on 3750x stack?

[BillClarkCC]

Have a x5 switch stack of 3750x switches.  I need to physically move the the last switch farther down in the rack to make room for some cable management arms.  Because of this, I need a longer stacking cable for the "homerun" from the last switch back up to the first.  Since this is an existing stack that is already fully configured, can I hot swap that cable or do I need to shutdown the stack before replacing the stacking cable with a longer one?

[Seb Rupik]

Hi there,

check the stack ring status with the command:

sh switch stack-ring speed

...if is says stack ring configuration is 'Full', then it is safe to remove a stack cable without powering down any switches or the stack

cheers,

Seb.

[BillClarkCC]

It does show as "Full" for the config.  Ring speed is 32G and the protocol is StackWisePlus

[Seb Rupik]

Then in my experience you are good to break the stack ring and replace the stacking cable.

Perhaps as one final pre-staging step make sure all stacking cable thumb screws are tight! ... but not with a screwdriver!

cheers,

Seb.

[balaji.bandi]

I need to physically move the last switch farther down in the rack  - given the information, i take this as the 5th switch.

here is the steps :

1. Move the users Port from Switch 5 to any other free ports - if the user accepted down time then that will be beneficial

2. Write the config on master switch of stack

3. take the config always out of the box, if you not done so, this is always good practice.

4. turnoff the Switch5

5. remove the stack cable and power cable ( also any patch cable to remove from front)

6. Move the switch to the bottom of the rack as per requirement.

7. connect the new stack length cable source and destination switch.

8. Turn on the Switch 5, wait for the switch to the boot  and join the stack

9. show switch and see the switch is joined stack.

10. any user device connected and test and close off the work.

Make sure do this in maintenance window is suggested since you are working Physically with the kit.,

[Leo Laohoo]

Before you start, can you post the output to the following command: 

show platform stack ports history 

[BillClarkCC]

Switch#/     Lost Sync       # times Link    # Changes
Port#          Events                Not OK         To LinkOK
--------- ----------- ------------ ----------
1/1                     0                       0                   1
1/2                     0                       0                   1
2/1                     0                       0                   1
2/2                     0                       0                   1
3/1                     0                       0                   1
3/2                     0                       0                   1
4/1                     0                       0                   1
4/2                     0                       0                   1
5/1                     0                       0                   1
5/2                     0                       0                   1

[Leo Laohoo]

Thanks for the output.  This tells me the stack ring is not "broken" or half-duplex. 

Personally, I have done a lot of changing ONE (1) stacking cables on a live stack without any outage(s). 

It can be done easily. 

1. Before I start, I make sure all the rest of the stacking cables are finger tight and none of them are wobbly. 
2. Make sure all the power cables are secure. 
3. IMPORTANT:  Make sure I have a console cable connected so if any of the remaining stacks break I know immediately.
4. Remove the target stacking cable. 
5. Replace the stacking cable with a new/longer one.  

[Joseph W. Doherty]

I recall (?) for 3750 series switches, Cisco recommends against connecting two powered on switches using a stack cable.  I don't recall any mention of disconnecting a stack cable between two powered on switches, but what applies connecting is a bit more likely to also apply to disconnecting.

I also recall (?) it's fine to have one switch powered on, i.e. they both don't need to be powered down.

If what I recall is correct, to migrate just a single stack member, you would only need to power it off, leaving the rest of the stack powered on.  Once you disconnect and reconnect the powered off switch, repower it and it should rejoin the stack.

Some "gotchas",  if the stack member to be moved is the active master, you may "blip" the stack's network activity, how much also depends on your stack configuration.

Also you want to insure all your stack members are dual connected before you power off the one stack member, otherwise you may partition the stack.

Lastly, you're only asking about the data stack, not the (optional usage) power stack, correct?  If not, don't recall what limitations there are for changing those connections beyond the power cables are (not well known) limited to the power they can carry between stack members.

[BillClarkCC]

Correct, this is for the data stack, NOT the power stack.  I'm leaning more and more towards powering off the last switch in the stack, disconnecting the one "homerun" cable, moving the switch where it needs to go and then attaching the longer "homerun" cable then powering that switch back on.  I'll do a config backup first before anything else, just to be extra careful.  Once that moved switch is powered up I'll check out the status of the stack and go from there.