I'm trying to find out the stacking capabilities and limitations around the newer 3850 XS switch. Based on the Data Sheet it says we can stack ther 12XS and 24XS. Is there a limit to the number of switches we can have in the stack and are there any compatibility issues stacking these with the older gig models.
Up to 9 Cisco Catalyst 3850 switches can be stacked together to build single logical StackWise-480 switch since Cisco IOS XE Release 3.3.0SE. Prior to Cisco IOS XE Release 3.3.0SE, up to 4 Cisco Catalyst 3850 switches could be stacked together.
Cisco Catalyst 3850 Series Switches FAQ
Catalyst 3850 stacks are limited to support up to 32 ASICs. Catalyst 3850-12X48U and 3850-24XU have 4 ASICs in them, therefore the limit with homogeneous MultiGig models is 8 stack members.
The Catalyst 3850 MultiGigabit switches can be stacked with nonMultiGigabit Catalyst 3850 switches as long as they do not exceed the 32 ASICs limitation.
I have not seen any other specific limitation for the WS-C3850-12XS-S or WS-C3850-24XS-S models as they should be backwards compatible and stackable with all Cisco Catalyst 3850 switches. You may want to open a TAC case if you have any issues with the stacking of these models.