Multi-homed connectivity represents the most redundant of all configurations when connecting an organization to the internet. It involves multiple CE routers connecting to multiple ISPs.
This requires the use of PI (provider-independent) IP addresses. The CE routers advertise the same address space to all ISPs. Routes are exchanged with the ISP: the customer learns routes from the BGP cloud via the ISP and the ISP advertises your PI address space to the rest of the internet.
Multi-homing has two advantages:
- It increases the reliability of the connection to the internet;
- It increases the utilization of connections to the internet as it allows for load-sharing and failover.
Stuck-in-Active: Journal of an IT-Network Administrator 