Source IP used in Recursive DNS Lookup
While we all know that DNS Recursive server will not use end user IP address for DNS query, it is also very important to note that the IP address used from Local DNS to authorize DNS server may not be the IP of local DNS server as well. For example： End user config 8.8.8.8 as his Local DNS Server, and issue multiple DNS requests from the same client; on the Authorize DNS server, we observed the source IPs for incoming requests are NOT 8.8.8.8 at all; but appeared to be some other IP subnet that belongs to google. 74.125.0.0 /16 Further testing shows these IPs are not responding to DNS queries (but pingable) so this appears to be some source IPs the DNS Anycast 8.8.8.8 will use to fetch the response from Authorize Server. This is important because: First, some GSLB or DNS server actually will attempt to store the entry of [ received source IP and Response sent back ], and might use this entry for further DNS Response persistence. But clearly we could see per IP ho...