3750 switch stack implementation

[hamidul.islam]

Hi.

We have two stacks of switches. In each stack we have 3 members now. All switches are 3750 [WS-3750-48PS-S] and the os version is 12.2. All the switches are now active and in operation and all ports are assigned to different VLANS.

I have to take a switch out of a stack and add it back to the other stack. That is after the changes one stack will have 2 switches and other stack will have 4 switches. The switch that I am going to replace has prority 1 and the stack where I am going to add has priority [15,10 and 5].

When I add the switch to the new stack will it automatically get the configurations from the stack master?

Will the  existing configurations of the switch will conflict with the new configurations?

Thanks

[Shashank Singh · Accepted solution]

Hi Hamidul,

In a switch stack, master switch is responsible for synchronizing the configuration on all member switches. As the new switch will join the stack as the member, its existing configuration will be automatically and permanently overwritten with the configuration of the stack master. There will not be any conflicts between the existing and new configurations.

Hope this helps.

Shashank

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[hamidul.islam]

Thanks for the information.

To avoid the worst case, Can I insert the startup configuration in the switch in advance and then add it to the stack? What is the process to do that?

Another question, once the switch is removed from the stack, will the stack master automatically configure that change? I mean the ports of the replaced switch that were assinged to different VLANS will be released from the configurations.

[Shashank Singh · Accepted solution]

Hi Hamidul,

Configuration need not be copied manually to the switch before adding it to the stack as it gets automatically synced after it joins the stack. However if you still wish to do that, you can download the existing configuration from the stack master to a TFTP server and upload it to the standalone switch's running-config. Configuration can also be manually copy pasted on the switch's CLI in global configuration mode. Please be informed that not all the configuration can be reused like this. For example, AAA configuration involving cryptographic keys cannot be copy pasted from one switch to another.

Once a member switch is removed from the stack, master automatically removes all the related configuration like interface level config and vlan assignments.

Hope this helps.

Shashank

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[hamidul.islam]

Thanks a lot.

[hamidul.islam]

What is a provisioned switch?

I can see the following configurations in my switch:

switch 1 provision ws-c3750-48p
switch 2 provision ws-c3750-48p
switch 3 provision ws-c3750-48p

Does this mean I have provisioned switch?

If I remove and add that switch back to another stack then do I have to include the following command before adding to the stack?

switch stack-member-number provision type

and what will happen if I don't issue the above command before adding?

After removing a switch from a stack do I have to issue the following command at the stack master to remove this configurations?

no switch stack-member-number provision type

[Shashank Singh]

Hi Hamidul,

Provisioning is a way of telling the stack master as to what model of switch is being added to the stack and what will be its switch number in the stack. In your case, all three switches in the stack were provisioned before being added.

In case you want to add switch 3 from this stack to another stack, it is advisablee to provision this switch on the new stack before adding it. Suppose you want to add this switch as switch 4 in the new stack, issue the following on the stack master of the new stack:

switch 4 provision ws-c3750-48p

Verify if the stack master is ready to accept this switch as the member by issuing the 'show switch' command. Once you see the switch provisioned you can go ahead and add the switch to the stack.

If provisioning for the new switch is not done, it will take the lowest available switch # automatically after being added to the stack.However, it is a best practice to provision the switch before adding it.

On the old stack master, you can issue the 'no switch 3 provision ws-c3750-48p' to remove the provisioning but this is optional.

Hope this helps.

Shashank

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[hamidul.islam]

I want to clarify my understandings on some of your informative guidelines. You have provided me very valauble information and it's helping me to get clear concepts on switch stack.

You mentioned:

In case you want to add switch 3 from this stack to another stack, it is advisablee to provision this switch on the new stack before adding it. Suppose you want to add this switch as switch 4 in the new stack, issue the following on the stack master of the new stack:

switch 4 provision ws-c3750-48p

What I have understood from your explanations is:

I should add the following command into the new stack master in advance before adding the switch to that stack and not on the replaced switch itself: Am I right?

                                 switch 4 provision ws-c3750-48p.

What the above command means in repect to the master switch? I mean what message does it provides to the new switch master in advanced?

You mentioned:

Verify if the stack master is ready to accept this switch as the member by issuing the 'show switch' command. Once you see the switch provisioned you can go ahead and add the switch to the stack.

After I issue the above command in the new stack master,

From what information of the "show switch" command output, I can verify that the stack master is ready to accept the new switch? Can you give an example for that? Will it add additional information  on the "show switch" output for the switch that it's going to accept or add in the stack?

I can get the follwing output from my present stack: How do you identify if a switch is provisioned switch from the following output?

sh switch
                                               Current
Switch#  Role      Mac Address     Priority     State
--------------------------------------------------------
*1       Master    004a.7b1b.1621     15        Ready
2       Member    002c.8aab.2255     10        Ready
3       Member    0015.749a.4599     1         Ready

I got the following information from the running configurations:

switch 1 provision ws-c3750-48p
switch 2 provision ws-c3750-48p
switch 3 provision ws-c3750-48p

I appreciate your valuable information. Actually I have lots of doubts on the stack mechanism implementation and want to clarify those before the actual change.

Thanks.

[Shashank Singh · Accepted solution]

Hi Hamidul,

Please find the answers inline:

I should add the following command into the new stack master in advance before adding the switch to that stack and not on the replaced switch itself: Am I right?   switch 4 provision ws-c3750-48p.

Yes, this command needs to be issued on the new stack master and not on the replaced switch.

What the above command means in repect to the master switch?I mean what message does it provides to the new switch master in advanced?

This command tells the master switch that there is a ws-c3750-48p model switch which will be added to the stack as switch number 4. Even if this command is not issued, the master allots the lowest available number to the new switch, but this is a best practice and is more useful in stacks where not all switches have exactly similar hardware.

Verify if the stack master is ready to accept this switch as the member by issuing the 'show switch' command. Once you see the switch provisioned you can go ahead and add the switch to the stack.How do you identify if a switch is provisioned switch from the following output?

Once you provision the new switch on the stack master this output will look like:

                                               Current

Switch#  Role      Mac Address     Priority     State
--------------------------------------------------------
*1       Master    004a.7b1b.1621     15        Ready
2       Member    002c.8aab.2255     10        Ready
3       Member    0015.749a.4599     1         Ready

4       Member    0000.0000.0000     1         Provisioned  <<<---------

This means that the new switch has been provisioned on this stack and that master has the knowledge that switch 4 may be added to the stack in future.

Hope this helps answers your questions.

Shashank

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[hamidul.islam]

Hi Shashank

Thanks once again for providing such wonderful information. That's helping me a lot.

I have some other questions regarding the backup or alternative plans in case of failue.

Question 1:

What's the approximate time for a stack switches to come into stable state after a removal or addition is done? Can we observe those changes at the LED?

Question 2:

I already downloaded the master switch startup configuration using the tftp server.

Since my switch is already a part of a stack and If I want to add the configuration of new stack in advance into that switch before adding it in the stack, what would be the best way of doing that? It would be very nice if you can write those into steps.

Question 3:

Even if I include the configurations before the switch is a new member of the stack, will the added switch once again synch itself from the master switch configurations once its a member of that stack?

Question 4:

During the adding or removing of the stack wise cables, one cable should always be attcahed between the ports of non replacing switch. Am I right?

I have attached an image file for connecting the stackwise cables between switches. Can you please tell me if any of them will be a good choice to connect 2 switches or is there any standard pocedure?

Thanks

Hamidul

[Shashank Singh · Accepted solution]

Hi Hamidul,

Question 1:

What's the approximate time for a stack switches to come into stable state after a removal or addition is done? Can we observe those changes at the LED?

Approximate time should be somewhere around 5 min for the new switch to come online after joining the stack as member. LEDs of the switch will depict the changes during this time.

Question 2:

Since my switch is already a part of a stack and If I want to add the configuration of new stack in advance into that switch before adding it in the stack, what would be the best way of doing that?

The best way to put new config on a standalone switch is to bypass startup config using the password recovery procedure:

http://www.cisco.com/en/US/products/hw/switches/ps628/products_password_recovery09186a0080094184.shtml

However, there is no point adding the configuration in the standalone switch because the configuration will anyways be overwritten once the switch is added to the new stack. For example, interface gi1/0/1 in a standalone switch will become gi4/0/1 after this switch joins as member # 4. Similarly other local configurations are overwritten with the master configuration.

Question 3:

Even if I include the configurations before the switch is a new member of the stack, will the added switch once again synch itself from the master switch configurations once its a member of that stack?

Yes it will sync again with the master and hence there is no point putting any config on the switch beforehand.

Question 4:

During the adding or removing of the stack wise cables, one cable should always be attcahed between the ports of non replacing switch. Am I right?

I have attached an image file for connecting the stackwise cables between switches. Can you please tell me if any of them will be a good choice to connect 2 switches or is there any standard pocedure?

One cable should always be attached between switches to maintain stacking, other can be removed and added to the new switch. Stackwise cables should be connected in criss cross manner as in picture 2.

Cheers,

Shashank

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[hamidul.islam]

Hi Shashank,

Thanks a lot. I really appreciate your feedback.

Best Regards

Hamidul

[hamidul.islam]

Hi Shashank,

One more question related to removing the switch from the stack. Will be there any LED activities on the master and member switch after a switch member is removed from the stack and all required cabling is done? or Do I have to give "reload" command on the master switch after removal to synch the changes?

Thanks

Hamidul

[Reza Sharifi]

Hi Hamidul,

Follow these steps to remove a member from your stack:

Remove a Member from the Stack

Complete these steps to remove a member from the stack:

1. Make sure that the stack is fully           connected so that, when you remove the member, the stack will be at           least in half connectivity, and do not partition.

2. Power off the member to be removed.

3. If the member was the stack master, the stack master election will           occur, otherwise no election will occur.

4. Remove the StackWise cables from the member and close the stack          ring.

5. Issue the command show switch to verify           the stack membership.

http://www.cisco.com/en/US/products/hw/switches/ps5023/products_configuration_example09186a00807811ad.shtml#stack5

HTH

Reza

[hamidul.islam]

Hi Reza

My question was:

Will be there any activities on the LED display panel of the stack after the change is implemented ie after a switch is removed from the stack? To be more precise can I observe any LED activities during the sync process after switch is removed from stack?

Thanks

Hamidul