5 switches in one Stack - How

[205000jag]

Hi All,

I have 5 Cisco switches 4 of them are 3750 Series and 5th switch is 3750 G series, 1st 4 switches are part of stack and 5th is not.

Design for 4 stack switches is :

Switch 1 Connect to Switch 4

Switch 1 also connects to switch 2 with a 2nd cable

Switch2 connects to switch 3

Switch3 connects to switch4

Can I remove the cable from second port from the switch4 which is connected to switch1 and plug switch 5 to switch4 and remove cable plug to 2nd port of the switch5.

If do the above is there any specific configuration which I need to do?

What is the down time I am looking at.?

Regards

[jfraasch]

Would pre-configure the switch 5 to make sure it does not take over master relationship.

My experience says this is a no downtime situation. Just adding another switch to the stack.

James

[205000jag]

Thanks James,

preconfigured means configure switch5 with the same IP which is using for stacked switches,

for downtime, do you think when I remove cable from the 4th switch whic is connected to switch1 any effect that time??? and connect to switch5 then.

is there way to know whic 1 is the master switch...?

[jfraasch]

The switches share the same ip. Shouldnt have to configure that.

From each of the switches you should be able to do a "show switch" command and that will tell you if it is the master. There are a few other options with that command that will tell you more.

You can config which switch number you want your switch to be. Possible numbers are 1-9. Here is the relevant information:

Tips to Add a Switch as a Slave to the Stack

To add a switch, as a slave, to a stack, complete these steps:

Note: Make sure the switch that you add into the stack has the same IOS version as the switches in the stack. Refer to Catalyst 3750 Software Upgrade in a Stack Configuration with Use of the Command-Line Interface to upgrade the IOS in a catalyst 3750 switch.

1.

Change the switch priority of the switch to be added to "1".

switch stack-member-number priority new-priority-value

Note: This step is optional, but it will make sure that the switch has fewer chances to become a stackmaster in the future.

2.

Power off the switch that is to be added.

3.

Make sure that the stack is fully connected so that, when you connect the new switch, the stack will be at least in half connectivity and does not partition.

4.

Connect the new switch to the stack with the StackWise ports.

5.

Power on the newly added switch.

6.

After the new switch comes up, issue the command show switch to verify stack membership.

[205000jag]

Thanks for the details james,

its all make sense, but as I mentioned above 4 stack switches are 3570 series with IOS 12.1 and 5th non stack switch is 3750 G series with IOS 12.2

Now If I simply unplug the 2nd stack cable from the sw4 and plug to sw5 and 2nd on sw5 connect to sw1 as I mentioned the design above ...with no commands will it work?

[Giuseppe Larosa]

Hello Sohail,

are these the same switches we have discussed about in other thread in lan forum?

I don't know if it is possible to stack swiches with a so different IOS version.

I would keep it separated if it is the same scenario discussed in the other thread.

Hope to help

Giuseppe

[205000jag]

HI Giuseppe,

No, these are similar but different switches same company but different site.

I think its not possible with with 2 different IOS.

[jfraasch]

I also believe it must be same IOS. I think it can be different model though...as long as is still 3750 series.

James

[hobbe · Accepted solution]

it will not work or rather it is not built to work that way.

You can have different 3750 hardware, but it is designed to have one and only one IOS.

so if the switches ios is an old one start with upgrading all the switches to the same IOS then (that will cause a reload) Then you can add the single switch to the stack.

Adding the switch should not cause any downtime however that said I would do it out of office hours since I have seen it crash even though it should not when adding switches to a stack.

and of course make a backup of the config in the switches first otherwise you might get a not so nice surprise, hopefully the master will still be of the stack, but then you will need to reconfig the switch you are adding.

dont forget to set prioroty to the masterswitch that are master in the stack today.

HTH

[vvasisth]

I understand that you require instruction on how to add/ remove a cat3750 to an existing stack.

First off, if a new switch needs to be added, it must have the same IOS image version as that of the existing 3750 in the stack. This avoids the version mismatch issue. To do so, the new switch to be added must already have the image loaded to it same as the ones on the stack. This link has all necessary procedures when managing switch stacks:

http://www.cisco.com/univercd/cc/td/doc/product/lan/cat3750/12220se/3750scg/swstack.htm

One important note though, make sure the switches that you add to or remove from the switch stack are powered off.

This is because:

Adding powered-on switches (merging) causes the stack masters of the merging switch stacks to elect a stack master from among themselves. The re-elected stack master retains its role and configuration and so do its stack members. All remaining switches, including the former stack masters, reload and join the switch stack as stack members. They change their stack member numbers to the lowest available numbers and use the stack configuration of the re-elected stack master.

Removing powered-on stack members causes the switch stack to divide (partition) into two or more switch stacks, each with the same configuration. This can cause an IP address configuration conflict in your network. If you want the switch stacks to remain separate, change the IP address or addresses of the newly created switch stacks. If you did not intend to partition the switch stack:

a. Power off the new switch .

b. Reconnect them to the original switch stack through their StackWise ports.

c. Power on the switch.

===============

The action you are planning to perform should not cause any downtime till the time there is one stack cable connecte from the switch to the stack or else the switch will be out of stack and wont function as a single unit.

Regards,

Varun