Cisco’s 3560 is a multilayer switch, designed to operate well at both layer 2 and layer 3. Due to its dual nature, however, Cisco had to allocate memory in a way that wouldn’t hinder operation in either mode out-of-the-box.
Out of the box, the 3560 has its memory allocated to support learning lots of MAC addresses and lots of unicast IP routes. If you know you’ll be using a 3560 as primarily a L2 or L3 device it makes sense to adjust the memory allocation accordingly. That’s done with a single command:
Switch1# conf t Switch1(config)# sdm prefer routing Switch1(config)# end Switch1# show sdm prefer The current template is "desktop default" template. The selected template optimizes the resources in the switch to support this level of features for 8 routed interfaces and 1024 VLANs. number of unicast mac addresses: 6K number of igmp groups + multicast routes: 1K number of unicast routes: 8K number of directly connected hosts: 6K number of indirect routes: 2K number of policy based routing aces: 0 number of qos aces: 512 number of security aces: 1K
Look here to see the differences between default, routing, and VLAN mode. Keep in mind that a reload is necessary to apply the changes.