try to bond links from different ISPin reference to:
"External BGP neighbors normally sit on directed connected networks.When one has multiple parallel links the a load balancing technique is to use loop back address in the configuration for the EBGP neighbor. Static routes are configured pointing to the loopback address on the far-side neighbor.I would not recommend you try to bundle links from different ISP if using over these links. You have to use the EBGP-multi-hop feature and trying to figure out the hop count to prove to be a very interesting exercise."
- Which Router will be suitable for bonding 2 or 3 Dsl cable connection? - Networking & Security (view on Google Sidewiki)