How to add new 3750 into existing stack ?

[cjrchoi11]

I have one 3750-48TS swtich with multi-VLAN and static routing table and want to add new 3750-12S and make it as master.

Q1) Can I just add the new 3750-12S switch with clean configuration ?

Q2) If yes Q1, who's master? the existing 3750-48TS?

Q3) If yes Q2, how is assigned the stack number? 3750-48TS as f1/0/x and 3750-12S as g2/0/x?

Q3) If I want to the new 3750-12S as master, can I change priority of the existing 3750-48TS to "10" and reload both switches?

Q4) If yes Q3, what happen the stack number? same as Q3 or reverse of Q3(3750-48TS as f2/0/x and 3750-12S as g1/0/x).

Thanks in advance,

[alagrawa]

Hi,

To add a new switch, make sure the new switch is powered down, then connect the stack cables and then power the new switch up. When the new switch powers up, it will come up as switch # 2.

A1. Yes, you can add the new 3750 switch with clean config. But make sure it is powered down before adding. One thing to make a point of though.. the switches need to run the same software code to be in a stack. The existing switch will try to upgrade/downgrade the code on the new 3750 to match its own code. There are a few caveats to this, hence if you prefer, you can upgrade/downgrade the code on the new switch to the same code as the existing switch.

A2. The existing switch will remain the master. The master cannot be preempted.

A3. The existing switch is most probably switch# 1. The new switch when it comes up in the stack will look for the lowest number available. Hence it will become switch # 2.

A4. Yes, change the priority of existing 3750 to 10 and reload both switches. Now switch # 2 will become the master.

A5. stack numbers remain same. existing switch will remains switch # 1. new switch will remain switch # 2.

regards

-Alok

[jlopezjim]

A4. I think that the switch with the higher priority will be elected as master. So you must change the priority of the new switch (switch 2), not the old switch (switch 1).

regards.

[alagrawa]

sorry, i made a slight mistake with A4. I initially thought the default priority is 15. hence changing the priority of the old switch to 10 would have resulted in the new switch having higher priority.

However i just checked up the following link.

http://www.cisco.com/univercd/cc/td/doc/product/lan/cat3750/12225sea/3750scg/swstack.htm#wp1153255

The default priority is 1. Hence as jlopezjim pointed out, the priority of the new switch should be changed to a higher value to make the new switch the master.

My apologies for the mistake and thanks for pointing it out.

regards

-Alok