Just was looking around at EDNS support by Google. To find how it supports and how packet looks like I created a test NS records for dnstest.anuragbhatia.com pointing to one of test server (18.104.22.168). I wasn’t running any DNS server on the server. Just ran quick tcpdump.
At server end:
sudo tcpdump ‘port 53 and dst 22.214.171.124’ -nn -vvv -w sample.pcap
Then I forcefully triggered DNS queries via Google’s recursor using:
dig @126.96.36.199 dnstest.anuragbhatia.com
At server end dump was captured. In wireshark came across the packet:
Packet dump > DNS Query > Addition records > <Root> Type OPT > Option C Subnet – Client Subnet this shows client subnet of BSNL from which I queried. 🙂
This is a very important project pushed by Google, OpenDNS etc to help CDNs (which are based on DNS resolution) perform optimally when end users use non-ISP based recursors. You can read more about project here.