In a brand new out of the box switch, is the IOS already installed or it is auto installed when we power on the switch.

  • What distinction are you making between "installed" and "on there somewhere but not installed", and why does the distinction matter? – TessellatingHeckler Jun 1 '16 at 23:53
  • i will be replacing some old switch with brand new switch, so my question was if the new switch that i am going to replace with will have IOS installed in it, and i dont have to deal with the IOS installation process and just start configuring the switch. I went through the deployment guide of the switch and it showed the process of extracting the bundle file and then installing in the switch. The installation also included the license installation procedure (which made me more confused). – user25763 Jun 2 '16 at 16:33
  • Yes, they come from Cisco ready to run. Nothing need be done to pass traffic in a default situation. – Ricky Jun 2 '16 at 19:40

Yes, IOS is installed on out of the box switches. If you buy them all at the same time and the same place (and they're the same model) then they will most likely have the same IOS version.

Having the same (or very close) version helps when you're stacking the switches (using the stacking cables in back to turn 2 to 9 switches into a single unit). If the version numbers are too far apart, the switches will not stack and you may need to upgrade the IOS on the older versioned switches manually. There's an auto upgrade feature but it doesn't always work like I would expect it to. :)

The point here is that even though the switches might be stacked and act as one unit, each switch still has and needs its own version of IOS. Even when upgrading a stacked set of switches, you need to copy the IOS on to each separate switch. The following link is for 3750 switches and there may be a newer one for 3850s but I doubt it will be much different. This contains all sorts of commands and instructions for stacking upgrading and copying IOS files between switches:


  • That's true if bought from Cisco (or authorized partner/reseller). From eBay or other greyer markets, there's no telling how they'll arrive. – Ricky Jun 2 '16 at 4:36
  • Good point. If you buy grey market it's possible you'll get a switch with no IOS and no license to get it from Cisco. – RSS Jun 2 '16 at 14:41
  • Yes, my company bought it from authorized partners – user25763 Jun 2 '16 at 16:31

New switch comes with installed IOS, it depend on your requirement whether you need need that IOS or not, you can downgrade or upgrade IOS as per your infrastructure need.

Also you if you need layer 3 features you need to upgrade switches license to IP service.

  • "iOS" is Apple's mobile OS, but "IOS" is Cisco's OS. – Ron Maupin Jan 22 '19 at 23:24

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