RFC3484のDestination Address SelectionのRule 9で選択してるんだろ。 正しい動作。DNSラウンドロビンによる負荷分散は時代遅れ。 Rule 9: Use longest matching prefix. When DA and DB belong to the same address family (both are IPv6 or both are IPv4): If CommonPrefixLen(DA, Source(DA)) > CommonPrefixLen(DB, Source(DB)), then prefer DA. Similarly, if CommonPrefixLen(DA, Source(DA)) < CommonPrefixLen(DB, Source(DB)), then prefer DB.
Source(D)は We write Source(D) to indicate the selected source address for a destination D. For IPv6 addresses, the previous section specifies the source address selection algorithm. Source address selection for IPv4 addresses is not specified in this document.
