Confgiuration of 3750 stack

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Feb 19th, 2009
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We have two standalone 3750 switches with the same version.If we connect them with stack cable, the configuration of two switches would be kept the same. I think it is the configuration of master switch. My question is:

Would the original configuration of member switch be removed? one is the port settings. Is it only changed interface number like from g1/0/1 to g2/0/1 and kept the other paratemters?

Another one is the global settings. For example, we created two port-channel (Po1 and Po2)orginally in the different switch with different vlann information. Once they be stacked, both Po1 and Po2 of the member switch would be removed,correct?

Thanks for your help!

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ccannon88567 Thu, 02/19/2009 - 12:51
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After stacking them with the stackwise cable/cables - Whichever one you power up 1st will be the Master and will copy it's configuration to the other switch.

In other words, power up the one you want to be a master and it will write it's config to the other when it is subsequently powered up.

Giuseppe Larosa Thu, 02/19/2009 - 12:57
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Hello Huan,

your understanding is correct and it is good practice to make these conservative assumptions.

a good starting point is:')">

you can reduce the effects of the merge by synchronizing the vlan configuration on the two standalone switches before the merge.

It is very important to influence the master switch election so that the intended switch will be the master.

You can do that with stack priority

switch stack-member-number priority

We had to remove a stack configuration and if I remember correctly the switches retained part of the configuration they had.

But here it is the opposite.

Hope to help


LUIGI PIETRONAVE Tue, 03/31/2009 - 12:12
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Hi Giuseppe,

hope You remember me. How are You ?

Can You explain me how configurations are saved into a stack ?

I mean: stack master hold the stack configuration on nvram, I suppose, but how about other stack members ? The config are keept on sync on all nvrams ?

I ask this because a customer of us has a 3750 stack and after a reload all config was lost, like if a "member" without config was elected master and overwritten the old master config ( thinking it was booted later ) .

Had You any suggest or any idea ?



Leo Laohoo Tue, 03/31/2009 - 15:13
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Hi Luigi,

When you configure a 3750 stack, you are configuring FROM THE master 3750. When the configs are saved, the master will propagate the configuration to all the members.

In your issue, when one of the 3750 was booted, did all the switches in the stack lost the config or was the one switch lost the config?

LUIGI PIETRONAVE Thu, 04/02/2009 - 01:23
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Hi and thanks for the reply.

I've a 2 switches stack. The customer was doing some maintenance on the rack so i'm not sure if there was a power down on both switch or only one of them.

What i've seen is that after the outage the stack was up, but accessing via console the switch propesed the "configuration dialog"




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