what does XL mean or stand for in Cisco models, like 2900 XL, 2924 XL, etc.
I hope you are not planning to include any of these xl seris in your network as these are end of sales model.
as far as xl goes, i think azoulflak is correct and if you wandering whats clustering technology now :)
I noted this quote from cisco doc for your reference -
Cisco Switch Clustering technology - All Catalyst 2900 XL switches support Cisco Switch Clustering technology, which allows users to configure, upgrade, and troubleshoot up to 16 Catalyst 3550, 2950, 3500 XL, 2900 XL, 2900 LRE XL and 1900 Series switches from a Web browser and single IP address.
check out the below URLs for more info :-