Best way to migrate

[Louis Adams]

Hi,

I currently have 2 cisco 3750X stacked switches and I need to replace them with 2 new cisco 3850 switches.  What is the easiest way to accomplish this?  I thought of configuring the 3850 stack with basics, then connect to the 3750 to pass vlans.  Then copy individual port configurations and then shutdown 3750 and bring up the 3850 stack with all the same configs of the 3750.  

Thoughts?

[Iulian Vaideanu]

Two switches is not that much... if there's room in the rack for the 3850s somewhere close to the 3750Xs (so that all cables can be easily moved between them) then I'd just pre-configure the new stack and simply move the cables.

This works better if it's mostly UTP (fibers take a bit longer to move, because you have to pull out the patch, then pull out the SFP) - I've recently done this (replacing a switch) and it took less than 3 minutes for ~40 populated RJ45 ports.

[Louis Adams]

yes the are close enough to transfer the cables.  Just really need to understand if I where to duplicate the settings interface vlans etc, with actually having the vlans on the switch, does this matter or will it work.  That is why I was thinking I would have to configure the 3850 first connect to switch environment (to get all the vlan database) then copy all the configs of the 3750 to the 3850 offline then power off the 3750 and then bring on the 3850. 

Does this make sense?

[chawilki · Accepted solution]

Building on what Lulian said, I would preconfigure the 3850s.  If the vlan database is large it would be easier to configure the 3750s to pass the vlans.  I would be very careful in configuring VTP in your production network, but it would make the transition a bit easier.  Hope this helps.

[Louis Adams]

Yes,

That is what I am doing.  I also notice the 3850 are a cat os.  So preconfigure the switch, then connected to the 3750 pass vlans via VTP Version 3.   Then I will take it offline duplicate all the port settings and IP settings and then switch it over.  I have to be careful and set a Bridge ID for the spanning tree, that is one gotcha I might had missed, since the 3750 I am replacing is the root switch.