February 7th, 2013, 02:35 AM
Force BIND to use EDNS
Is it possible to force a BIND DNS server (that is configured for forward-only) to use EDNS when forwarding the original DNS queries to other DNS servers in case the EDNS support is not advertised in the original query?
The problem is that the dns resolver making the original query doesn't support the EDNS so in case the response is over 512 bytes TCP needs to be used. However, it is be preferred that the EDNS would be used between the forward-only DNS server and the other DNS servers.
My understanding is that if the BIND server receives query that doesn't indicate support for EDNS, it is not used in the forwarded queries either (even if it's enabled in the BIND server).
And Im wondering is there any way force the (forward-only) BIND server to use the EDNS or is the only way to have the support already in the original query?
The BIND version used is 9.4.