14 Apr

EDNS support by Google’s Public DNS

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 ( I wasn’t running any DNS server on the server. Just ran quick tcpdump.


At server end:

sudo tcpdump ‘port 53 and dst’ -nn -vvv -w sample.pcap


Then I forcefully triggered DNS queries via Google’s recursor using:

dig @ 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.

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