load balancing

Channel bonding (two ethernet cards, one IP) comes with Tiger if I remember correctly.

It will only buy you extra availabilty if one of the ethernet cards, the cable to the swith or one switchport dies.

Nothing to do with HA-setups with redundant machines and infrastructure.

Also, be aware that the switch you connect those two network interfaces to will need to know about the bonded connection. Most consumer-grade switches don't support this kind of thing.

If you don't maintain the network, make sure you have a talk with whoever does before you try this.