Some of the limitations of IOS SLB include:
No support for load balancing of flows between clients and real servers that are on the same local area network (LAN) or virtual LAN (VLAN). The packets being load balanced cannot enter and leave the load-balancing device on the same interface.
Does not support coordinating server load balancing statistics among different IOS SLB instances for backup capability.
You could use the following link for the details:
http://www.cisco.com/en/US/products/sw/iosswrel/ps1833/products_feature_guide09186a0080080fee.html#1015337
Hope this information is useful.