Network engineers will sometimes speak of connections to their ISP(s) in terms of single homed, dual homed, single multihomed, and dual multihomed. Here is a breakdown and clarification of what this terminology means:
- Single Homed (1 link per ISP, 1 ISP)
- Dual Homed (2+ links per ISP, 1 ISP)
- Single Multihomed (1 link per ISP, 2+ ISPs)
- Dual Multihomed (2+ links per ISP, 2+ ISPs)
Obviously, if you are a datacenter or large enterprise, dual multihomed is definitely costly but the way to go. A dual multihomed setup can help with redundancy, but just as importantly decisions can be made, for instance by BGP (Border Gateway Protocol), on the best path to reach various destinations.. Below are some graphical examples.