6.1.3.4 Multihomed Hosts

When the host name-to-address function encounters a host with multiple addresses, it SHOULD rank or sort the addresses using knowledge of the immediately connected network number(s) and any other applicable performance or history information.

DISCUSSION:

The different addresses of a multihomed host generally imply different Internet paths, and some paths may be preferable to others in performance, reliability, or administrative restrictions. There is no general way for the domain system to determine the best path. A recommended approach is to base this decision on local configuration information set by the system administrator.

IMPLEMENTATION:

The following scheme has been used successfully:

1. Incorporate into the host configuration data a Network-Preference List, that is simply a list of networks in preferred order. This list may be empty if there is no preference.

2. When a host name is mapped into a list of IP addresses, these addresses should be sorted by network number, into the same order as the corresponding networks in the Network-Preference List. IP addresses whose networks do not appear in the Network-Preference List should be placed at the end of the list.