After you have configured a test address, you need to ensure that this address is not used by applications. Otherwise, if the interface fails, the application is no longer reachable because test addresses do not fail over during the failover operation. To ensure that IP does not choose the test address for normal applications, mark the test address as deprecated.
IPv4 does not use a deprecated address as a source address for any communication, unless an application explicitly binds to the address. The in.mpathd daemon explicitly binds to such an address in order to send and receive probe traffic.
Because IPv6 link-local addresses are usually not present in a name service, DNS and NIS applications do not use link-local addresses for communication. Consequently, you must not mark IPv6 link-local addresses as deprecated.
IPv4 test addresses should not be placed in the DNS and NIS name service tables. In IPv6, link-local addresses are not normally placed in the name service tables.