Cisco 3750 stack with SMI IOS

Unanswered Question
Mar 15th, 2010

We have 4 switches WS-C3750G-48TS (PowerPC405) with IOS (C3750-IPBASE-M), Version 12.2(35)SE5,  configured in a stack.

Now we need these switches to support BGP4 and WCCP v2.

Can I upgrade only two switches to EMI IOS and leave another two switches to SMI IOS?

Is very expensive to upgrade from SMI to EMI.

Or,

Can I buy two  more switches 24 ports (WS-C3750G -24TS-E1U) with EMI IOS and put all 6 switches on a single stack?

Thank you

Sam

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Reza Sharifi Mon, 03/15/2010 - 08:24

Hello Sam,

The IOS for the entire stack has to be the same. Instead of buying 2 new switches get the license for the existing stack.

HTH

Reza

samuelpetrescu Mon, 03/15/2010 - 08:29

Thank you for answering.

The price for an EMI license is almost the same as a new Switch 3750 24 ports with EMI IOS.

Reza Sharifi Mon, 03/15/2010 - 08:36

Sam,

If you get 2 new switches then you have stack them separately and not mix them with your existing once since the IOS images are different..  Talk to your sales rep on the licensing price.  You may get a dipper discount since you are stacking them.  I know with the 6500 dual sup the only charge you for one IOS since one is active and the other one is stand-by.

HTH

Reza

hadelmahmoud Thu, 03/17/2011 - 07:57

I think you can upgrade only two switches to EMI as per the attached document

Master Switch Election
The stack behaves as a single switching unit that is managed by a master switch elected from one of the member
switches. The master switch automatically creates and updates all the switching and optional routing tables. Any
member of the stack can become the master switch. Upon installation, or reboot of the entire stack, an election
process occurs among the switches in the stack. There is a hierarchy of selection criteria for the election.
1. User priority—The network manager can select a switch to be master.
2. Hardware and software priority—This will default to the unit with the most extensive feature set. Catalyst 3750
switches with Enhanced Multilayer Software Image (EMI) versions take precedence over Standard Multilayer
Software Image (SMI) versions.
3. Default configuration—If a switch has pre-existing configuration information, it will take precedence over
switches that have not been configured.
4. Uptime—The switch that has been running the longest is selected.
5. MAC address—Each switch reports its MAC address to all its neighbors for comparison. The switch with the
lowest MAC address is selected.

also

Cisco IOS Images Must Be Identical
The Cisco StackWise technology requires that all units in the stack run the same release of Cisco IOS Software. When
the stack is first built, though, the units can have SMI and EMI version differences. This will automatically cause the
EMI versions to become the master switches so the stack can use routing functions. However, the first time you
upgrade the Cisco IOS Software release, all units will be required to run the same SMI or EMI version as the master.

note in the above document it stated on the same release even if they SMI and EMI

Leo Laohoo Thu, 03/17/2011 - 14:48

Can I upgrade only two switches to EMI IOS and leave another two switches to SMI IOS?

No you can't.  Here's the reason:

1.   Firstly, the entire stack has to be using the SAME FEATURE SET because you can't program, for example, BGP routing on an IP Base switch.  Remember that your ENTIRE STACK operates as one.

2.  Secondly, presume that you did manage to get this running and you need TAC's help.  They'll see what you've done and, most likely, raise their hands up in the air and tell you that they won't support a setup like that.

3.  Lastly, it won't work because the stack will see that the new members are operating in a higher feature set and during a crash, will cause the entire stack to operate in "limbo" and totally un-responsive.

It is better to upgrade your stack to IP Services or DO NOT USE the IP Base software. 

hadelmahmoud Sat, 03/19/2011 - 02:24

first I'd like to thank you for your reply but as you read in the above post ,theoretically you can mix the stack between SMI and EMI

note in the master switch election

2. Hardware and software priority—This will default to the unit with the most extensive feature set. Catalyst 3750
switches with Enhanced Multilayer Software Image (EMI) versions take precedence over Standard Multilayer
Software Image (SMI) versions.

also note that:

When
the stack is first built, though, the units can have SMI and EMI version differences.

so if I have new solution not upgrade I think I can mix the stack between SMI & EMI

your fast reply is highly appreciated

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