Fragmented DNS Packet

binddomain-name-systemip-fragmentationmtu

The DNS response against my domain is 1228 bytes long and I need the packet to get fragmented in 3 packets. To achieve this I have set the MTU at name server (bind9 running on the machine) to be 500. TO verify that MTU is set to 500, I ping from the name server with 600 bytes it gives me error that packet is too long (since MTU is 500 bytes). But when I query the name server I get back the complete reply 1228 bytes in one fragment. I need the packet to be fragmented to run some tests.
I am using dig from the client side to query to my name server and if use noedns option from the client side I get the reply with DNS truncated bit set and then OS sends the same query over TCP.
Any suggestion how could I get IP fragmentation.

Best Answer

Are you sure that the response is 1228, that's huge ... check what dig thinks the size of the response is.

dig google.co.uk
...

;; WHEN: Sun Feb 22 11:55:42 2015
;; MSG SIZE  rcvd: 46

Note the last line is the size of the DNS response.

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