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stackable switches

Hi all

can anyone tell me these questions about the stackable switches

1, do you have a master switch, that when you telnet to it, you are telnetting to the master

2.can you replace a switch in the stack whilst they are powered up, and can they automatically load the correct image and config onto the new switch?

3.are they plug and play, does the stack automatically know when switches are added? you have 1 ip for the stack, and how is this added?

5.are they cascaded in a total loop for redundancy?


Hi Carl

This all relates to the stackwise plus on the 3750/60 series.

1. Yes you have a master switch that has the IP address that you telnet to.

2.Yes you can replace a switch at any time without powering down the stack and they will load the IOS from the master.

3. Yes the master will update the stack info when a new switch is added.

4. Yes it is the normal process of adding an IP to a switch.

5. Yes the switches are daisy chained.

hi there, how do you set which switch is the master?

-how would I configure some ports on switch number 2?

-what is the throughput of the stack cables?

-when I add the ip address, would I just do it as normal then and this would apply to all switches ?

-how many switches can you have in a stack


1. Switch with the highest priority becomes the master (u can set this to any value between 1 - 15)

2. The ports on the member stack will be preceded by the switch number.. for eg on a 2 member stack, the ports on the second switch will be tagged as 2/0/1 , 2//0/2 etc

3. For a normal 3750 it is 64 Gbps. If you are using 3750E then it is 128 Gbps

4. Yes

5. You can have upto 9 switches in a single stack



The switch with the highest switch stack priority wins which you set with

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

Otherwise it goes to the election proces :-

Here is the election process

The switch that is currently the stack master

Note: When stacks merge, the elected stack master would have been the master of one of the merged stacks.

Note: When stacks partition, the stack master of the original stack will be the master of its partition.

The switch with the highest stack member priority value

Note: Cisco recommends that you assign the highest priority value to the switch that you prefer to be the stack master. This ensures that the switch is re-elected as stack master if a re-election occurs.

The switch that uses the non-default interface-level configuration

The switch with the higher Hardware/Software priority. These switch software versions are listed from highest to lowest priority:

Cryptographic IP services image software

Noncryptographic IP services image software

Cryptographic IP base image software

Noncryptographic IP base image software

Note: Switches that run Cryptographic or IP services image will take a longer time to load than Non-Cryptographic or IP base image. When you power on or reset an entire switch stack, some stack members will not participate in the stack master election. This is because stack members that are powered on within the same 20-second time frame participate in the stack master election and have a chance to become the stack master. Stack members that are powered on after the 20-second time frame do not participate in this initial election and only become stack members. At times, switches with lower software priority can become the stack master, but all stack members will participate in the stack master re-election.

The switch with the longest system up-time

The switch with the lowest MAC address

To config gig interface 4 on 'stack member 2' you would enter this command under global config mode:-

interface gigabitethernet2/0/4

3750 it is 64 Gbps full duplex. If you are using 3750E then it is 128 Gbps full duplex and with the E series they dont send local traffic through the ring as they do with the non E series.

When you add the IP address, it will apply the config to the master switches config as file.

You can have nine switches in total.

I would suggest reading the two documents below:

Catalyst 3750-E and 3560-E Switch Software Configuration Guide, 12.2(46)SE

Here at the chapter 5-1 Managing Switch Stacks you find the most answer.

Master election can be controlled by priorities.

If you stack switches you get the port numbering with stack-number/module/port.

Catalyst 3750-E and 3560-E Switch Command Reference, Release 12.2(46)SE

Only the throughput is a other story. First the stack is a classic token ring. The 3750 and 3750G has 32Gbit bandwidth depend the technologies.

With changing the protocol was bandwidth increased of theoretical 64Gbit. Effective are 48Gbit more realistic.

If you mix the standard series or -G with 3750E it fall back to 32Gbit.

An other point is the commercial part. A stack can contain up to 9 switches but between 2-4 devices you reach the price of well equipped 4507R-E

hth andy

Leo Laohoo
VIP Community Legend

The new 2975 and 3750/3750-E can operate with just one (1) management IP Address. The 2975 is a pure Layer 2 appliance but the latter can do multi-layer switch.

If left by default, during the first boot, the switch will "elect" who will be the master. The switch with the LOWEST MAC Address is the master.

As with previous post, you can manually configure the switch to be the master.

The beauty of this technology is that you just configure the first/master switch with the correct configuration and when members are added, the configuration is "shared" among each and everyone of them. IOS, on the otherhand, needs to be manually updated (

For more information regarding the StackWise/StackWise Plus, please refer to the following slide presentation:

Is this helpful?

hi there, can someone show me the command to make to switch master?

if the master is lost, can you set a secondary master?

also is it possible to sync the IOS in them, do you really have to do it manually ?

Hi Carl

Re read my earlier post

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