Question about Stacking Cisco WS-C3750X-24S-S

Question: Existing Switch (stacked with another 3750G-24TS on same code) WS-C3750G-24TS: running 12.2(35)SE5 IP services (not universal image)

New Switch Cisco Catalyst 3750: WS-C3750X-24S-E : expect it will come with latest code, universal image.Are there any problems stacking 3750TS with 3750 XSeries. Whats the least disruptive way to do this?

Answer: The most important part is to match up the code level on the switches or they won't work together. I think it's more of a version match than the nitty gritty ipservices versus universal (with the IP services license).

show ver on a mixed stack:

Switch Ports Model              SW Version            SW Image                
------ ----- -----              ----------            ----------              
*    1 30    WS-C3750X-24       12.2(55)SE            C3750E-UNIVERSALK9-M    
     2 28    WS-C3750G-24TS-1U  12.2(55)SE            C3750-IPBASEK9-M        


One gotcha when mixing G with X series is the SDM template. The SDM template is a method used to distribute resources on the switches for use with different categories of processes. A quick Cisco search will get you the details, but it comes down to templates that are geared towards routing, switching, or a mixture (default) of the two. Each one opens up possibilities while also closing others. For example, the default allows you to run routing protocols, but only to a certain extent. If you were to configure a policy route, the command would not return an error, but also would not show up in the running config nor take effect. You would have to set the SDM template to routing for PBR to be truly configurable. Now for the gotcha... the SDM template names can be slightly different between G and X series - even just a capitol versus lower case letter. Whichever switch is the master as bootup determines the SDM template to push to all other stack members. Another thing is that the different switch types have different amounts of resources so the X series will be able to handle more in each template than the G series. I can't remember if all the switches went with the lowest common denominator, or if you're plainly running the risk of running out of resources on the G switches before the X switches.

The above gotcha may have been corrected in the new versions of code, but a couple years ago I went through this and had to settle with the default SDM template which limited some of the routing I was hoping to accomplish. If you're being affected by this, you will see the error at bootup.

Cisco 3750X  more information and the configuration, visit http://www.3anetwork.com/blog/ for more.