這裡說明 DNS proxy 的行為

( p.s. 不是每個 DNS proxy 都是這樣做 )

CASE 1 :

若 DNS proxy 第一個 nameserver 是 IPv4 DNS server

Query A over IPv4 packet --> DNS proxy --> Query A over IPv4 packet

Query AAAA over IPv4 packet --> DNS proxy --> Query AAAA over IPv4 packet

Query A over IPv6 packet --> DNS proxy --> Query A over IPv4 packet

Query AAAA over IPv6 packet --> DNS proxy --> Query AAAA over IPv4 packet

CASE 2 :

若 DNS proxy 第一個 nameserver 是 IPv6 DNS server

Query A over IPv4 packet --> DNS proxy --> Query A over IPv6 packet

Query AAAA over IPv4 packet --> DNS proxy --> Query AAAA over IPv6 packet

Query A over IPv6 packet --> DNS proxy --> Query A over IPv6 packet

Query AAAA over IPv6 packet --> DNS proxy --> Query AAAA over IPv6 packet

由上面 2 個例子來看 , DNS proxy 送出的封包是根據 nameserver 來決定

若 nameserver 是 IPv4 , 則 DNS proxy 送出 IPv4 封包

若 nameserver 是 IPv6 , 則 DNS proxy 送出 IPv6 封包

CASE 3 :

假設 DNS proxy 有 2 個 nameserver

若 DNS proxy 第 1 個 nameserver 沒有回應

則 DNS proxy 會改用第 2 個 nameserver

注意 ! 是沒有回應才改用下一個 nameser

待續 

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