Cisco Stackwise

(Geert D) #21

Hi Rene,

First of all, your work is amazing, thank you very much!

I used Stackwise for a while in several branch office designs and I like the advantages about it.

some weeks ago I had a discussion with a consulting farm, they claim that Stackwise is still running spanning-tree on the switch backplane

and would not converge fast due to the spanning-tree. It seems odd to me and never heard about it.

Do you know if that is the case and have you ever seen some info about this?


Thanks a lot!


(Rene Molenaar) #22

Hi Geert,

Glad to hear you like my work!

Spanning-tree doesn’t run on the stackwise backplane, not sure where they got that from :slight_smile: They use some proprietary mechanism to create a “bidirectional closed loop path” (that’s what Cisco calls it).


(seth s) #23

Quick question, how would I know what physical interface on stacked switches is on the CLI. If I have a stack of 9 switches, and my admin says unplug the cable to g3/0/20, what switch am I physically unplugging if I saw 9 switches stacked? Would I have to know the MAC of switch 3 and look at the sticker at the back of the switch?

(Rene Molenaar) #24

Hi Seth,

Normally the stack members are numbered from 1 to 9. Here’s an example for two switches in a stack:

SW1#show ip interface brief | include Fast
FastEthernet1/0/1      unassigned      YES unset  down                  down    
FastEthernet1/0/2      unassigned      YES unset  down                  down    
FastEthernet1/0/3      unassigned      YES unset  down                  down    
FastEthernet1/0/4      unassigned      YES unset  down                  down    
[output omitted]    
FastEthernet2/0/1      unassigned      YES unset  down                  down    
FastEthernet2/0/2      unassigned      YES unset  down                  down    
FastEthernet2/0/3      unassigned      YES unset  down                  down    
FastEthernet2/0/4      unassigned      YES unset  down                  down    
[output omitted]

FastEthernet 1/x/x is SW1 and 2/x/x is SW2. In your case, it should be the third switch from the top.


(seth s) #25

So best practice is to have your master at the top of the stack and physically label each switch? I am only wondering this because we are supposed to cross the stackwise cable to each switch, like stack1 connector connects to stack2, the stack1 connectoe connects to stack2. So on and so forth until the last stack switch connects his stack1 connector to stack2 on the master. Maybe the IOS of the master knows that anything connecting to my stack1 slot will be g2/0/1 and anything connecting to my stack2 slot will be gX/0/1.

(Rene Molenaar) #26

When a switch joins the stack then it will pick the lowest available member in the stack.

If you have 5 switches and you want to number them from top to bottom then it might be a good idea to configure them like this:

switch 1 priority 15
switch 2 priority 14
switch 3 priority 13
switch 4 priority 12
switch 5 priority 11

This ensures that the same switch is always elected as the master and that the interface numbers will match.

If needed, you can also rename them later:

switch 4 renumber 5

This will rename switch number 4 to 5.

(seth s) #27

Thank you for your input, it has helped a lot. I found this,
If you push the button on the front of the switch and select stack, it will tell you the member number and how many switches are in the stack. Neat!

(Chheang C) #28

Hi Rene,

For the stackwise switch, Can I force slave to master by command-line.

Best Regards,

(Rene Molenaar) #29

Hi Chhayheng,

The best way to do this is to increase the priority of the slave switch. This will ensure it will become the new master when there is a re-election.


(Chheang C) #30

Hi Rane,

When they re-election, or we need to restart switch to make them re-election ?


(Philipp K) #31

The election order is incorrect, non-default configuration will decide the master before the hardware/software priority:

(Rene Molenaar) #32

That is a good complete list indeed, thanks.

@Chhayheng The link provided by Philipp also explains when the (re)election is performed:

  1. When the whole switch stack is reset1
  2. When the stack master is reset or powered off
  3. When the stack master is removed from the stack
  4. When the stack master switch has failed
  5. The switch stack membership is increased by if you add powered-on standalone switches or switch stacks.


(Mohammad Hasanuz Zaman) #33

Hlw Rene,

Amazing. Could you please let me know in which situation will we use STACKWISE/VSS ? What is the advantage of using it ?


(Andrew P) #34

It has to do when you want additional levels of fault tolerance. An example of this might be where you have a server that has multiple network cards. In the server’s operating system, say Windows 2012 R2, you have the option of having these cards work together (in Windows it is called NIC Teaming). If you have a switch using VSS or Stackwise you can plug each of these network cards into a different physical switch. When you do this, if a switch port fails, or even an entire switch, the Windows server will be unaffected.

(Patrick W) #35

Hi Rene,

In a stacking scenario with 6 switches, I have configured the top to be “switch 1” and added switches down the rack in sequential order.

My question is: would it be better to manually set the priority of the other stack members, so that one of the others at the bottom does not become the new master? or does it matter once the previous master is gone?

Thank you,


(Lazaros Agapides) #36

Hello Patrick.

Whenever you configure a stacking scenario, it is always best to manually select the switch that you want to be master. It doesn’t matter which switch in the stack becomes master as far as its position is concerned (i.e. bottom, top or middle of stack). As it says in Cisco’s official documentation:

Cisco recommends that you assign the highest priority value to the switch that you prefer to be the stack master. This ensures that the switch is re-elected as stack master if a re-election occurs.


Once the previous master is gone, then the next highest priority is chosen. However, it is always a good idea to reevaluate the priorities and change them MANUALLY accordingly whenever you split or merge a stack (remove or add switches). This way, you are always sure about which switch is master.

I hope this has been helpful!


(Abhishek D) #37

hi Rene,

You showed 2 ports on each switch :

on SW 1 : port 1 and port 2
on SW 2 : port 1 and port 2

and showed a yellow X. can you plx explain in further ?

so we need 2 stack cables ?

first cable between port-1--------port-2 of switch 1 AND
second cable between port2-----------port1 of switch 2 ?

is this how it is …if yes why it cant p-1 — p-1 AND P-1 — P-2 ?


(Andrew P) #38

I don’t think the diagram is intended to be an “X” so much as to show you which ports are connected together. Your interpretation is correct–you need two cables (for redundancy) such that SW1 Stack 1 connects to SW2 Stack 2, and SW1 Stack 2 connects to SW2 Static 1.

As to why Cisco chose to implement the cabling this way, I don’t really know.

(Networklessons Admin) split this topic #39

19 posts were merged into an existing topic: Cisco Stackwise

(Abhishek D) #40

Hi Rene

Great article. If we have stakced switch in network, do we need to consider STP here (in below diagram specifically).

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