3750 Stack replacement

Unanswered Question
Apr 20th, 2010

I have several different stacks, consisting of 3750G-24PS and 3750G-24TS, with a cold spare 3750G-24PS.  If a 3750G-24TS fails and I use the 3750G-24PS as a replacement, will the 3750G-24PS retain the same config as the 3750G-24TS?

Will the same hold true if my spare is the new 3750X-24PS-S?

Thanks,

Dennis

I have this problem too.
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allan.thomas Tue, 04/20/2010 - 10:56

Hi Dennis,

Unfortunately it is not as straight forward as that, essentially if the provision switch type differs to that of the switch you are adding to the stack the default configuration will apply to the switch and not the provisoned port configuration even though it may have a the same switch number.  Refer to the following guidelines regarding adding a switch a the stack, particularly the section titled the effects of adding a provision switch to a switch stack:

http://www.cisco.com/en/US/partner/docs/switches/lan/catalyst3750/software/release/12.2_40_se/configuration/guide/swstack.html#wp1178950

The following is taken from this guide:

Scenario
Result

The stack member numbers and the switch types match.

1. If the stack member number of the  provisioned switch matches the stack member number in the provisioned  configuration on the stack, and

2. If the switch type of the provisioned  switch matches the switch type in the provisioned configuration on the  stack.

The switch stack applies the provisioned configuration to the  provisioned switch and adds it to the stack.

The stack member numbers match but the switch types do not match.

1. If the stack member number of the  provisioned switch matches the stack member number in the provisioned  configuration on the stack, but

2. The switch type of the provisioned  switch does not match the switch type in the provisioned configuration  on the stack.

The switch stack applies the default configuration to the provisioned  switch and adds it to the stack.

The provisioned configuration is changed to reflect the new information.

The stack member number is not found in the provisioned configuration.

The switch stack applies the default configuration to the provisioned  switch and adds it to the stack.

The provisioned configuration is changed to reflect the new information.

The stack member number of the provisioned switch is in conflict with an  existing stack member.

The stack master assigns a new stack member number to the provisioned  switch.

The stack member numbers and the switch types match:

1. If the new stack member number of the  provisioned switch matches the stack member number in the provisioned  configuration on the stack, and

2. If the switch type of the provisioned  switch matches the switch type in the provisioned configuration on the  stack.

The switch stack applies the provisioned configuration to the  provisioned switch and adds it to the stack.

The provisioned configuration is changed to reflect the new information.

The stack member numbers match, but the switch types do not match:

1. If the stack member number of the  provisioned switch matches the stack member number in the provisioned  configuration on the stack, but

2. The switch type of the provisioned  switch does not match the switch type in the provisioned configuration  on the stack.

The switch stack applies the default configuration to the provisioned  switch and adds it to the stack.

The provisioned configuration is changed to reflect the new information.

The stack member number of the provisioned switch is not found in the  provisioned configuration.

The switch stack applies the default configuration to the provisioned  switch and adds it to the stack.

Regards

Allan.

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dvaggalis Tue, 04/20/2010 - 11:29

Okay, I think I'm getting it.  My original design would not have the cold spare provisioned with the correct member number, but would have the "new, out-of-the-box switch"  default stack member number of 1.

1.  If the failed switche's member was #2, wouldn't the replacement switch assume member #2, because it is the lowest number available?

2.  If the failed switch was a 3750G-24TS and the replacement was a 3750G-24PS, since it has the same port count, would it not applies the provisioned configuration and add it to the stack as member #2?

3.  Does the above still hold true if my cold spare is a 3750X-24PS-S?

Thanks again,

Dennis 

allan.thomas Tue, 04/20/2010 - 13:28

Hi Dennis,

1.  If the failed switche's member was #2, wouldn't the replacement switch assume member #2, because it is the lowest number available? NO, this number is already provisioned, and would therefore assume the next.

2.  If the failed switch was a 3750G-24TS and the replacement was a 3750G-24PS, since it has the same port count, would it not applies the provisioned configuration and add it to the stack as member #2? NO, the switch-type is not the same and therefore the provisioned configuration would not apply.  In order for the configuration to apply the switch number and type have to match.  This follow reference was taken from the same guide under Switch Stack Membership, 'If you replace a stack member with an identical model, the new switch functions with exactly the same configuration as the replaced switch, assuming that the new switch is using the same member number as the replaced switch.'

3.  Does the above still hold true if my cold spare is a 3750X-24PS-S?  Only if the switch-type and member is the same, therefore a certain amount of manual intervention is required.  If the switch-type is the same, then ensure that the switch number is the same number as the switch being replaced.  The table I listed previously identifies the various scenarious.

Regards

Allan.

Hope this helps, pls rate helpful posts.

Leo Laohoo Tue, 04/20/2010 - 15:04

The only difference between the 3750G-24PS and 3750G-24TS is the Power over Ethernet.

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