adding 3750 to stack

[Patrick McHenry]

Hi,

I have two  3750s stacked and one 3750 standalone all in one data closet. The both have the same versions. I want to combine them to make one stack.

Questions:

How do I force the standalone to be the master? sw 1 priority XX(Higher then the existing stack)?

Both the stack and the standalone have management addresses. Would it be ok to delete the stack ip address? That way, the standalone(master's address will be the only management address)?

How should I connect the standalone 3750 to the stack? At present, the 3750 stack is connected via a cascade cable going from the stack 1 port of the top switch to the stack 2 port of the bottom switch.

Thanks, Pat.

[Leo Laohoo]

How do I force the standalone to be the master?

Use the command "switch 1 priority 15".  The highest value is "15" and this means that the switch with this value does NOT join the stack master election.

Both the stack and the standalone have management addresses. Would it be ok to delete the stack ip address? That way, the standalone(master's address will be the only management address)?
How should I connect the standalone 3750 to the stack? At present, the 3750 stack is connected via a cascade cable going from the stack 1 port of the top switch to the stack 2 port of the bottom switch.

The easiest way is this:

1.  Delete the config and the vlan.dat file from the 2nd switch;

2.  Power down the switch and leave the 1st switch powered up;

3.  Attach the stacking cable; and

4.  Power on the second switch

[Patrick McHenry]

I can't delete the config on ether of the switches - they are in production.

"Use the command "switch 1 priority 15".  The highest value is "15" and this means that the switch with this value does NOT join the stack master election. "

So, if I give the switches in the current stack, each a prioroty of 15, they will not be the master? This will unsure that the standalone will be the master when I add it?

[Leo Laohoo]

I can't delete the config on ether of the switches - they are in production.

I'm not recommending you deleting the config of both switches.  I'm recommending you delete the config of the switch that will JOIN THE STACK MASTER.  Leave the config of the stack master alone.  The slave switch's config needs to be deleted.

So, if I give the switches in the current stack, each a prioroty of 15, they will not be the master? This will unsure that the standalone will be the master when I add it?

No, configure this command to the STACK MASTER only.  Remember, when you're dealing with switch stacking, all the config is done on the stack master.  The slave switches, once joined, will synchronize or copy the config from the stack master.  This is why my recommendation to delete the config and vlan.dat file from the slave switch so it can join the stack harmoniously.

[Patrick McHenry]

Leolaohoo,

All the switches are in production. Not just the existing stack. The standalone is as well. When I join them, I want the standalone to be the master.

So, to make the standalone the master, I should give it a priority of 15?

The stack and the standalone have identical configs except for the interfaces(VLANs, speeds, duplex,) and management address and hostname. Will the standalone(master) write over the management address and hostname of the stack switches - but keep the interface configurations of the existing stack switches in tact?

Thanks, Pat.

[Leo Laohoo]

So, to make the standalone the master, I should give it a priority of 15?

Yes that's correct.

The stack and the standalone have identical configs except for the interfaces(VLANs, speeds, duplex,) and management address and hostname. Will the standalone(master) write over the management address and hostname of the stack switches - but keep the interface configurations of the existing stack switches in tact?

Ok, so you want to move your existing stack INTO the current stand-alone?  Ok, here's the trick.  It can be done.

Use the "switch X provision <3750 model number>" on the master stack.  This will enable you to pre-configure the ports of the new stack members BEFORE you let the stack members join.  Once you're satisfied with the config, attach the stack members to your stack master and power up the stack members in the order of your configuration.  This last bit is just a one-off.

Does this make sense to you?

[Patrick McHenry]

Thanks for the response Leoloahoo.

Could you please confirm that I understand?

So, my stack is confgured and in production and my standalone is configured and in production.

1) Give the standalone switch a sw priority of 15

2) Use the switch X provision command on the stack(this allows the stack to be configured before adding the new master)

3) Power down the stack and attach it to the new master in the order I want my interfaces to be ordered(fa1/0/1 switch then fa2/0/1 switch)

4) Power up the stack and the standalone should should become the new master.

Questions:

Should I also power down the standalone before adding the stack - and then, power them up in order - 1, standalone, 2, first member of stack then, 3, second member of stack?

Or, should I just power down the stack then, attach the stack, then power them up in order - 1, first member of stack, 2, second member of stack?

When they are all attached and up and running will the master be the member that's interfaces start with fa1/0/ then the second member's interfaces start with fa2/0/ and the third member start with fa3/0/?

If the previous question is true, and the members of the original stack change their interface numbers from fa1/0/1 to fa2/0/1 and fa2/0/1 to fa3/0/1, will this somehow shift the configs of the interfaces or with physical ports retain their configs?

Should I delete the management ip address of the stack before adding it to the new master or will this management ip be overwritten by the master and it's management ip will become the management ip for the stack?

Thank you and sorry for all the questions, Pat

[Leo Laohoo]

Let me see if I can answer your questions ...

Ok, here's how I would tackle this.  Let's make some premise ...

A.  Switch #1 is a stack;

B.  Switch #2 is a stand-alone and you want this to be your stack master.

Here goes ...

1.  Configure #2 as your stack master using the command "switch 1 priority 15";

2.  Next, pre-configure #1 into #2 using the command "switch 2 provisioning <3750 model number>" and/or "switch 3 provisioning <3750 model number>" and so on.

3.  In #2, configure the ports, VLANs, etc.  Because you have "provisioned" the switch you can start putting config.

4.  Once you are happy with what you are done to #2, ensure that #1 has the same IOS version and feature-set to #2;

5.  Erase the config of #2 stack.

6.  Power down #1 switch

7.  Connect members of #1 to #2 via the stack cable;

8.  Once #2 is populated with the switch members, apply power to the rest of the stack members one at a time and in the order of your stack.  This means that you power up stack member 2, wait for about 10 seconds, power up member 3, etc.

9.  Once the rest of the stack members have joined the stack, you can add "switch 2 priority 13", "switch 3 priority 11", etc.

You do not need to power down the #2 stack master when you add the rest of the stack members.  The stack members, however, need to be powered down before you attach the stacking cable.

If #2 interface identification is "Fast 1/0/XX" then its good.  If #2 interface ID is not what you want, "Fast 3/0/XX instead of Fast 1/0/XX", then you need to run a few extra commands:  switch renumber 1 and reboot.  This means that after the reboot, the #2 interface ID will be "1".

So when you attach the stack members to the stack master and power up the stack members one at a time and in order, stack member switch 2 will have an interface ID of "Fast 2/0/XX", stack member switch 3 will have an interface ID of "Fast 3/0/XX", etc.

Does this make sense to you?

[Patrick McHenry]

Leolaohoo,

I appreciate your efforts - but these switches are in production. Are you saying that it is impossible to combine these 3750s without having a blank config on both of them? In step 3 you say, "in the standalone switch configure ports vlans ect." The Stack and the standalone both are configured and in production. I want to combine them without deleting configs if possible.

With step 4 and 5, why would I configure the standalone(#2) then, delete it?

I'm getting lost in a labyrinth.

Thanks for your help, Pat.

[Leo Laohoo]

Are you saying that it is impossible to combine these 3750s without having a blank config on both of them?

Here's the deal ...

If you join a pair of 3750 togeter without power off the switch stack members the stack member switch(es) will reboot.

Ok?  So this is why I recommend you delete the config and power down the switch prior to joining the switch members to the stack.

With step 4 and 5, why would I configure the standalone(#2) then, delete it?

You pre-configure the switch stack members BEFORE they are joined to the stack master.  You do the pre-configuring on the stack master and NOT on the switch stack members.

[Patrick McHenry]

Leolaohoo,

altimately, I am trying to accomplish the combining of the stack and standalone with minimal downtime. Perhaps, only the amount of time they take to reboot.

Couldn't I do this:

1. Configure the standalone with a sw 1 priority 15.

wr mem

2. Configure the second switch in the stack with

sw 3 provisioning 3750 Model Number

sw 3 priority 11

3. Configure the first switch in the stack with

sw 2 provisioning Model Number

sw 2 priorority 13

Delete the crypto config, the management VLAN interface and the hostname.

wr mem

4.Attach the standalone to the stack - At that point the stack will reboot. And because of the config I gave the switches before attaching them, the standalone will become part of the stack and be the master sw 1 and the stacked switches will be sw 2 and sw 3 respectively.

Will this work?

Your last paragraph in the your last post doesn't make sense to me as I can't do any port configuration on the standalone switch for the interfaces that are on the stack switches. Do you mean I configure the switch priorities on the standalone switch before attaching them?

Thanks for your help, Pat.

[JohnTylerPearce]

Your last paragraph in the your last post doesn't make sense to me as I can't do any port configuration on the standalone switch for the interfaces that are on the stack switches. Do you mean I configure the switch priorities on the standalone switch before attaching them?

These are the following commands that Leo suggested.

switch 2 provision <3750 Model Number)

switch 3 provision <3750 Model Number)

After you type those in on the switch that is to be the stack master, you can configure the ports, even if the future stack members are not physically connected. The reason for this, is so you can configure everything beforehand, and when you connected the stack members that already have the configuration.

Depending on if you have gig/fa ports you would do the following on the stack master

int gi2/0/2

and or

int gi3/0/2

This is called prestaging.

As far as your last post, I would personally do it the way leo suggested, it leaves less room for error or weird things to come up.

[Patrick McHenry]

Thanks for clearing that up John. I was going in circles .

Leo, on the your 4th post of this thread, are your steps supposed to say:

5.  Erase the config of #1 stack.

6.  Power down #1 stack

instead of:

5.  Erase the config of #2 stack.

6.  Power down #1 switch

I don't think you intended to tell me to erase the config of the standalone after I had configured all the ports.

That being said, do I have to power cycle the standalone after I configure sw priority 15?

Thanks for all your help.

[JohnTylerPearce]

I don't think you will have to power cycle the standalone, I'm pretty sure the priority will become 15 once you enter that command.  On a side note, every standalone 3750 is it's own stack master. If you take a 3750 brand new OOB, it will be a stack of just 1 switch, that's why when you see the configuration it's

int gi1/0/x.

This means it's stack number 1. So it's the master by default. But I would still put in the command

switch 1 priority 15.

[Patrick McHenry]

Thanks John.

one more question. While getting ready to add the standalone to the stack, can I configure the standalone to have a priority of 15 and provision the other interfaces and configure those interfaces without any service interruption?

Thanks, Pat