One physical network can carry multiple logical networks. Moreover, we can use multiple physical networks at the same time in a host. In that environment, end-hosts might have multiple IP addresses and be required to use them selectively. Without an appropriate source/ destination address selection mechanism, the host will experience some trouble in the communication. RFC 3484 defines both the source and destination address selection algorithms, but the multi-prefix environment considered here needs additional rules beyond the default operation. This document describes the possible problems that end- hosts could encounter in an environment with multiple logical networks.