Stcking a 3750 switch 3

[glamprecht1]

I currently have one cisco 12 port 3750 that acts as the core switch for my entire network. I am not only out of ports but need to add redundancy to the core swtich. I would like to stack a second 3750 to the first. Then use the original 3750 switch's ip to manage both.
From what i am reading It sounds like i just connect them together with the backbone cable. From there the second switch is automatically configured. Is this true? The last thing that i want to do is to take down the entire network.
Is there more involved? It just sounds to easy.

 

[glamprecht1]

That should be "Stacking a 3750 switch"

sorry!!

 

[ADB100]

When you add the 2nd switch your original switch will appear to have had a module installed. You currently have ports Gig1/0/1 - 1/0/12, when you add the 2nd switch you will have Gig2/0/1 - 2/0/12 (assuming you are adding a 2nd 12-port Gig 3750 - 3750G-12S?). The stacking process will automatically number the new switch as 2 (although you could manually provision this if you wanted to).
Software versions should be identical, so check what's on the existing one and upgrade/downgrade the new one so they match (it will probably work if they don't match but for peace of mind do this as I know some versions are incompatible). Make sure you have the same feature set on both switches - if the existing switch is running IP Services then DON'T use IP Base on the new one. The reason is the Stack Master dictates what features run on the entire stack so if the Master has IP Services then the extra features IP Services gives you (multicast routing and the routing protocols EIGRP, OSPF & BGP) are available. If however you get a stack failure and the other switch has only IP Base and becomes the Master you will loose these features.
If you decide to upgrade the IOS when the stack has formed be aware that all stack members will be upgraded so IF you do decide to mix the feature sets within the stack then there will be license implications if you haven't purchased the appropriate licenses.

HTH

Andy

 

[DallasBPF]

Actually, having the problem of stacking with different IOS's... You will have a hell of time getting them to work with different IOS's, because the primary should copy its IOS over the new one. But this does not happen all the time, actually I spent several hours going from floor to floor breaking the link and upgrading them one at a time...

------------------------------------
Dallas, Texas
Telecommunications Tech
CCVP, CCNA, Net+

CCNP in the works

 

[ADB100]

Hi DallasBPF, I have upgraded a LOT of 3750 stacks over the past couple of years and I have never had any issues with upgrading IOS. I have hit issues with customers having existing stacks and trying to add new switches to the stack with different IOS versions. I know this can be a pain and can be a bit hit-and-miss as to whether it works or not. I generally make sure the new switch is running the same version as the current stack before attempting to join them.
Once they are all running the same IOS version then upgrading the stack as a whole has never (not even once) been a problem, for me anyway?


Andy

 

[glamprecht1]

Okay.. There is a 2 year difference between the two switches so we can safely assume that the new one has a newer IOS on it. ( I have not booted it up yet) The swtiches are identical in model so the only real difference should be the IOS.
Sounds to me like the course of action is to downgrade the new switch to match the old one. Once in the Stack then upgrade the master and that will automatically overwite the members.
This still sounds somewhat easy...
So the master (switch one) just automatially configures the second??
Just for fun...
What happens if the master swtich fails? Will the second one continue on?
Can this second swtich be added during bussinuss hours? will it cause any interuption with the master?
Thanks for all the posts so far!!

 

[ADB100]

Yes the 2nd switch just 'appears', as I said it looks like you have just inserted a module into slot 2 and ports Gi2/0/1 - 2/0/12 appear. Once it has been added to the stack though it gets some NVRAM parameters set that make it always be stack member 2, so if you decide later on to split the stack it remembers this. This is easily fixed though.
If the master fails the 2nd one assumes the master role - Once the stack is active any configuration changes get written to each stack member so any can assume the master role, however you should set stack priorities to ensure predictability.
One thing that does happen when a new master takes over is all the MAC addresses on the switch change which can be a pain, even though GARPs are sent for each SVI. A new feature was added 'Persistant MAC' that solved this issue, however this was only added in 12.2(35)SE.

Andy

 

[DallasBPF]

Dont get it either... there was no adding new switches to the stack, we were just upgrading the IOS's and once the primary was upgraded and rebooted the secondary's would freeze up... soooo that led me to cart my laptop around to each floor, break the stacks, and upgrade each one...

------------------------------------
Dallas, Texas
Telecommunications Tech
CCVP, CCNA, Net+

CCNP in the works

 

[VinceWhirlwind]

Configure your old switch to log at debug level to your syslog server, then add the new switch to the old one and watch your syslog.

It will tell you exactly what the status is with the upgrade.

Sometimes it will auto-upgrade, or sometimes you may have to manually make it happen.

If you want the newer IOS on the stack, you will need an outage to upgrade the old switch.
First, archive the IOS off the new switch and then onto the old one. Then add the new switch to the old one.

 

[ADB100]

Dont get it either... there was no adding new switches to the stack, we were just upgrading the IOS's and once the primary was upgraded and rebooted the secondary's would freeze up... soooo that led me to cart my laptop around to each floor, break the stacks, and upgrade each one...

That isn't how it's supposed to work. The Master downloads the code from the source (FTP/TFTP/HTTP etc) once it has it it upgrades itself and then sequentially upgrades each of the stack members (it can take a while if its a big stack). Once all the members are upgraded it symultaneously reloads all members (including itself) assuming you added the '/reload' to the 'archive upgrade-sw....' command?. The Master should not reload alone and before any of the members have been upgraded.
Maybe you had a bad IOS release or you just used the 'copy tftp flash' command to only copy the IOS image?

Andy

 

[DallasBPF]

tried the archive command first and it would fail in the download, so I just went with the copy tftp flash with the IOS...

------------------------------------
Dallas, Texas
Telecommunications Tech
CCVP, CCNA, Net+

CCNP in the works

 

[burtsbees]

I think you can tell if the IOS is zipped (.tar) in sh flash, then you would use the tar -xvf blablabla...wait...that's UNIX...sorry.
Whatever the command is...
If it is already a .bin, then you do the copy tftp flash.

Burt

 

[ADB100]

I think you can tell if the IOS is zipped (.tar) in sh flash, then you would use the tar -xvf blablabla...wait...that's UNIX...sorry.
Whatever the command is...
If it is already a .bin, then you do the copy tftp flash.

Doing it this way doesn't upgrade the stack members though, hence why DallasBPF had issues. You need to use the .tar file and use the command:

archive /download-sw /overwite ftp://x.x.x.x/software-release.tar

Andy

 

[burtsbees]

But if it is not zipped, would the archive/blablabla work? I would think you'd console into each switch...

Burt

 

[vipergg]

You can download to the indivdual members using a bin file , you just use "copy tftp: flash1: for say switch 1 then use
copy tftp: flash2: for switch 2 . If you do it this way then just use this as a boot statement.
boot system switch all flash:/<imagename> .

 

[DallasBPF]

well hell... that could have saved a LOT of walking around 7 different floors lol.... one tip I don't plan on forgetting!! =)

Thanks viper!

------------------------------------
Dallas, Texas
Telecommunications Tech
CCVP, CCNA, Net+

CCNP in the works

 

[vipergg]

This doc will get you get you thru most upgrades. If the new switch seems to freeze or not load then it is probably a version mismatch , it should tell you in the logs and their is a command to tell you that which I can't think of of the top of my head. That being said in most cases even in version mismatch mode the master usually will still "see" the secondary switch and you can just copy the image from the stackmaster down to the secondary switches . If you want to avoid all problems then just make sure the new switch has the same exact version to load in flash and then insert it powered off intot he stack.

http://www.cisco.com/en/US/products...guration_example09186a00804799d7.shtml#cfbin1

 

[burtsbees]

well hell... that could have saved a LOT of walking around 7 different floors lol.... one tip I don't plan on forgetting!! =)"

I like the exercise myself...lol

 

[glamprecht1]

So much good info here.

Last question...Can this be done during the day without fear of impacting the primary switch? This primary switch is basicaly a single core for the entire network.

I will back up the config and add the second switch to form the stack. I am just unsure if the primary needs to relaod or if the second switch can be added without impacting anything else.

I have successfully upgraded the IOS to match the first swtich so i feel that am ready to go. Just not sure if i need to plan for an outage or not.

Thanks Again.

 

[vipergg]

Make sure the new switch has the same ios version . Leave new switch powered off and hook up the stack cables then power on the switch . Technically it should not cause any problems but we all know how that works with cisco switches .