allow-query does not seem to be working

[Frank Even]

I have a group of servers serving out multiple addresses via anycast.  I've
been made aware that an IP outside of our network is hitting the boxes with
queries, and we're returning data to the client.

With allow-query and allow-recursion locked to our subnets, this outside
host is still getting responses, and I'm trying to figure out why.

named.conf snippet:

allow-query { mynets; };
allow-recursion { mynets; };

Yet in response to a host not from one of the subnets allowed, we're
getting requests and returning some kind of response:

# tcpdump -i any -nvv src $myhost and dst 156.154.100.3
tcpdump: listening on any, link-type LINUX_SLL (Linux cooked), capture size
65535 bytes
13:37:30.578020 IP (tos 0x0, ttl 64, id 5059, offset 0, flags [none], proto
UDP (17), length 81)
    $myhost.33941 > 156.154.100.3.domain: [bad udp cksum f39c!] 54976 [1au]
A? www.sparknewspaper.co.uk. ar: . OPT UDPsize=4096 OK (53)
13:37:30.578025 IP (tos 0x0, ttl 64, id 5059, offset 0, flags [none], proto
UDP (17), length 81)
    $myhost.33941 > 156.154.100.3.domain: [bad udp cksum f39c!] 54976 [1au]
A? www.sparknewspaper.co.uk. ar: . OPT UDPsize=4096 OK (53)
13:37:30.644502 IP (tos 0x0, ttl 64, id 5060, offset 0, flags [none], proto
UDP (17), length 79)
    $myhost.61737 > 156.154.100.3.domain: [bad udp cksum fef9!] 7832
[1au] A? silverstonepaint.co.uk. ar: . OPT UDPsize=4096 OK (51)
13:37:30.644505 IP (tos 0x0, ttl 64, id 5060, offset 0, flags [none], proto
UDP (17), length 79)
    $myhost.61737 > 156.154.100.3.domain: [bad udp cksum fef9!] 7832
[1au] A? silverstonepaint.co.uk. ar: . OPT UDPsize=4096 OK (51)
13:37:30.722628 IP (tos 0x0, ttl 64, id 5061, offset 0, flags [none], proto
UDP (17), length 68)


If an IP is not allowed as part of an "allow-query" statement, should the
name server still be returning any responses?

BIND version - BIND 9.8.2rc1-RedHat-9.8.2-0.47.rc1.el6
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