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Cisco 3750 - This Isn't Your Father's Old Switch! 

Added: 11/28/2005, Hits: 4,198, Rating: 0, Comments: 0, Votes: 0
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For those of you who have never used the Cisco 3750 switches, what are you waiting for? Oh, that whole price thing? C'est la vie! But for those of you who have the cash or work for a company that has the cash, these little switches are fantastic! They replace the old 2948G-L3 layer 3 switches, and have this wonderful 32GB stacking system that is just incredible. Ran out of switch space? No problem! Just add another switch to the stack, and it will seamlessly add itself to the switch. So, you can have up to 9 switches that are seen as one switch from a management point of view. Much better than the clustering.

But with each new technology comes the woes of learning...or the joys, depending on how much time you have to learn things. More of a woe when it is "on-the-fly" in a production environment. :)

As stated earlier, the neat thing about these switches is that you can add more switches to the stack and it is still only seen as one switch. The downside? They all have to be on the same version of software. No big deal, unless you ran into what I just did the other day.

I added a GB 3750 switch to a stack of two 10/100 3750 switches. This was to add GB functionality for a couple of new customers that need GB throughout their network. Not a problem, with the exception that the switch came with the 12.2.25SEB2 version of IOS. Well, the switches that I have had the 12.2.25SEAx version of the IOS on it. Ok, I thought, no big deal. I went to CCO to get the instructions on how to update a stack. I figured that because I need to update them all, I would simply update them to SED.

Uh...not so fast Sparky.

Because the third switch was not fully recognized in the stack, the stack would not update. Ok, I will updated the other two switches on the stack and get them all on the same version, then update the stack. Simple right?

Wrong again, Sparky.

When I tried to update the older switches in the stack to SEB2, the stack responded by saying it was already installed. Huh? Well, it is installed on one of the switches, so even though it isn't fully recognized by the stack, it is recognized enough to see that I am trying to update with a version that is already on one of the switches.

So, if you run into this situation, here is what you do:

1. Plug all the switches together with the 32GB wires in the stack.
2. Turn on all the switches that have the lower version of the IOS. Do not turn on (with a switch, this means plug in the power) the new switch. This keeps the third switch from being seen.
3. Update the stack to the same version of the new switch using the method described on the CCO site.
4. Reload the stack.
5. After the stack reloads, turn on the new switch.

At this point, the new switch should be fully recognized by the stack. Now, you can update the entire stack with the latest and greatest IOS version.

Back to work, Sparky!

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