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My company will upgrade two Cisco 3560G switches (an HSRP Active & Standby pair) to two Cisco 3750X switches in a stack.

I need to make a switch replacement procedure starting from removal of the Cisco 3560s switches until the Cisco 3750x switches are put online. I have googled it, searched the Cisco website, and searched various forums, but I couldnt find something to suit my needs.

My approach will be...

  1. Backup the standby 3560 config (traffic will flow through the active 3560).

  2. Remove the plug of 3560 and put in one 3750x. Configure 3750x to accept traffic and to be the stack master.

  3. Backup the config on the remaining 3560 and remove it.

  4. Plug in the second 3750x

  5. Configure it as stack member.

Please review this procedure and give advice. If you can point me to any vendor documentation that shows a step by step procedure for a switch upgrade like this, I would appreciate it.

  • Remember to click the up arrow next tohestok's answer - I assume that you found it insightful since you marked it as an accepted answer. – Jan Jun 26 '13 at 7:51
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I don't think you're going to see any website with direct step-by-step instructions on how to do this. There maybe a few blogs which speak to a blogger's personal experience....however, this is how I would approach it.

I'm going to assume that your current 3560Gs have L3 links to the core and an L2 link (or portchannel) between the two switches. I will also assume that you're using interface tracking to help swap HSRP states and pre-emption and etc...

While you are adding the 3750X to the original 3560G switches. All you would require is to extend the L2 link to the 3750X stack. You can pre-provision the 2nd 3750X and even have it running and connected when you do this entire process.
Then move the L3 uplinks from the standby 3560G to the first 3750X and ensure that HSRP is configured in order to facilitate the failover.
Once that is done...begin migrating your cabling/device cable to the 3750X stack.
Then move the final 3560G L3 link to the 2nd 3750X switch. You should now also be able to remove the L2 link between the 3750'ss and 2560's and power them off.

Since you're using HSRP - the 3750X's should become active under your control (via a priority change)

Finally, after you are left with just the 3750X in a stack-formation. You will no longer require HSRP to run between the two switches since the 3750X will really be seen as one switch all together. Ultimately, the end solution should have 2x L3 uplinks to your core or router, and the VLAN interface existing solely on the 3750X stack. I would also have the each of the L3 links attached to the separate 3750X switches as well.

This final solution should give you a more robust design from preventing spanning tree and HSRP timers from delaying your network re-convergence and allowing the routing protocol to do the upstream path selection instead of HSRP.

  • 3
    There is no universal consensus that stacking devices has positive or negative impact on the MTBF. Some believe that by using stacking you allow single software defect to impact both of the devices. – ytti Jun 26 '13 at 6:11
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    @ytti i have many co-workers who hate stacking as well. I believe the stacking cables and hardware in general has improved a bit on the X series than the original G and E series. I haven't been burnt by them yet but some of my co-workers hate it and refuse to deploy these in any shape/form today – knotseh Jun 26 '13 at 6:20
  • @hestonk I've had a lot of issues with our 3750X stacks, but once the initial setup is done... they have worked quite well. Had a run of bad cables/bad switches mixed in with issues in the stack setup (new switch would wipe out existing stack setup). After all was configured though, great experience. – some_guy_long_gone Jun 26 '13 at 16:35
  • I feel people are often too desperate to get rid of STP that they try anything. At we least we've been burned by stacking and REP. STP while nasty, is very old and proven code, it's pretty hard to out-perform it in terms of reliability. – ytti Jun 27 '13 at 8:55
  • I got the point now. Thank you for your great support. – Tsubasa Jun 28 '13 at 3:46

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