3750 series switches in a stackwise configuration

Answered Question
Aug 17th, 2009
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Hi,


we have 3 x fiber switches Model number : WS-C3750G-12S-S running IOS Version 12.2(25)SEB2 and they are all stack wised together.


We would like to connect a 4th switch to the configuration which will be a ws-c3750g-24ts-s1u which will have a blade chassis attached to it.


I have relatively little experience with switch stacking and would like to know if any compatibility issues are likely to arise with IOS versions / features?


Can anyone shed any light on this at all?


Any help appreciated... thanks!


Mario De Rosa

Correct Answer by Joseph W. Doherty about 7 years 8 months ago

"They have to be Desktop SDM templates don't they? "


Yes.


"I also understood that it is the Stack protocol version that needs to remain the same rather than the IOS version, is that correct? "


I believe that's true, although the best way to insure that is if the IOS versions are the same (although feature sets can differ).


"And lastly, can this 24port switch be added to the stack whilst online? Or will there be any downtime? "


I believe that also true although there's a procedure to follow which includes how the new switch should be configured before being added to a stack.


"I understand that the 2 stack masters will hold an election, so i need to make sure that the stackmaster of the existing stack wins don't I? "


The documentation for adding a stack member, I also recall, addresses that, and I believe normally a running and active stack master keeps its position. I.e. new stack member additions don't easily preempt it.


The configuration guide chapter "Managing Switch Stacks", has most details, e.g. http://www.cisco.com/en/US/docs/switches/lan/catalyst3750/software/release/12.2_44_se/configuration/guide/swstack.html. You might especially review the "Effects of Adding a Provisioned Switch to a Switch Stack" section. ([edit] BTW, just noticed, Collin posted same reference.)


More infomation about stack managagement can be found here: http://www.cisco.com/en/US/products/hw/switches/ps5023/products_configuration_example09186a00807811ad.shtml#number


Correct Answer by Collin Clark about 7 years 8 months ago

There are some things to check for such as the IOS major revisions must match. Here's a link on what to check for and how to provision a switch to make sure the installation goes smooth.


http://www.cisco.com/en/US/docs/switches/lan/catalyst3750/software/release/12.2_44_se/configuration/guide/swstack.html


Hope that helps.

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Correct Answer
Collin Clark Mon, 08/17/2009 - 08:04
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There are some things to check for such as the IOS major revisions must match. Here's a link on what to check for and how to provision a switch to make sure the installation goes smooth.


http://www.cisco.com/en/US/docs/switches/lan/catalyst3750/software/release/12.2_44_se/configuration/guide/swstack.html


Hope that helps.

marioderosa2008 Mon, 08/17/2009 - 08:16
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Thanks for the prompt reply!


I'll get stuck in to that article... cheers!

Joseph W. Doherty Mon, 08/17/2009 - 08:34
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One issue to be aware of, the C3750G-12S models support SDM templates that are not compatible with the other 3750 models. So, you need to insure they use a SDM template that is compatible.

marioderosa2008 Tue, 08/18/2009 - 02:19
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Hi Joseph,


yeah, i did read about the SDM templates. They have to be Desktop SDM templates don't they?


I also understood that it is the Stack protocol version that needs to remain the same rather than the IOS version, is that correct?


And lastly, can this 24port switch be added to the stack whilst online? Or will there be any downtime?


I understand that the 2 stack masters will hold an election, so i need to make sure that the stackmaster of the existing stack wins don't I?


Any help on the above points would be great.


Mario

Correct Answer
Joseph W. Doherty Tue, 08/18/2009 - 03:27
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"They have to be Desktop SDM templates don't they? "


Yes.


"I also understood that it is the Stack protocol version that needs to remain the same rather than the IOS version, is that correct? "


I believe that's true, although the best way to insure that is if the IOS versions are the same (although feature sets can differ).


"And lastly, can this 24port switch be added to the stack whilst online? Or will there be any downtime? "


I believe that also true although there's a procedure to follow which includes how the new switch should be configured before being added to a stack.


"I understand that the 2 stack masters will hold an election, so i need to make sure that the stackmaster of the existing stack wins don't I? "


The documentation for adding a stack member, I also recall, addresses that, and I believe normally a running and active stack master keeps its position. I.e. new stack member additions don't easily preempt it.


The configuration guide chapter "Managing Switch Stacks", has most details, e.g. http://www.cisco.com/en/US/docs/switches/lan/catalyst3750/software/release/12.2_44_se/configuration/guide/swstack.html. You might especially review the "Effects of Adding a Provisioned Switch to a Switch Stack" section. ([edit] BTW, just noticed, Collin posted same reference.)


More infomation about stack managagement can be found here: http://www.cisco.com/en/US/products/hw/switches/ps5023/products_configuration_example09186a00807811ad.shtml#number


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