Multihomed

A host which is said to be multihomed is one which has more than one network interface each of which has different IP addresses.

While such hosts are *supposed* to send all packets out an interface with a source address assigned to that interface, not all always do, and there are some valid reasons why that might happen.

Such hosts/sites will require special handling from BCP38 implementing access providers, but their number is generally small enough to make handling such things as manual exceptions a reasonable process.