ECLB is a feature of Catalyst switch code that allows a Catalyst switch to split flows over different physical paths. With this technology you can place multiple IPS appliances in on-a-stick mode, clustered on an EtherChannel, to split load among the sensors. This deployment results in, incremental IPS bandwidth increase for each IPS appliance you add to the ether-channel. So if you start with a single IPS appliance with a throughput of 500 megabytes (MB) and then add a second sensor with the same throughput capabilities to the EtherChannel, you will have 1 gigabyte of resulting throughput.
You should understand the following about deploying ECLB:
Although the ECLB name insinuates load balancing, it is not. It is actually load splitting. ECLB works by hashing the source and destination IP addresses of a flow to determine what physical port a flow should take when traversing the Catalyst.