On Aug 7, 2007, at 4:43 PM, Ask Bjørn Hansen wrote:
> On Aug 7, 2007, at 16:33, Chuck Swiger wrote:
>> Certainly BIND is doing round-robin within the result set:
>
> That's just your local cache rotating the same 14 IPs.
Nope, there is more going on. I just set up a test zone having 256
RR's via:
$TTL 86400
@ IN SOA localhost. hostmaster.localhost. (
1 ; serial
3h ; Refresh 3 hours
1h ; Retry 1 hour
30d ; Expire 30 days
1d ) ; Minimum 24 hours
@ NS localhost.
localhost A 127.0.0.1
$GENERATE 0-255 test A 192.168.1.$$
I then ran:
tcpdump -w tcp.dump -s 0 -i lo0 port 53 &
...and did several digs against this test.example.com. When the size
of the return results are bigger than 500 bytes, dig falls back to
using either EDNS0 over UDP or TCP. The TCP results returned all 256
values, rotating the order they are returned for each query.
The UDP results returned about 25 results (ie, which is what would
fit within the 500 byte limit), again rotating the result set so that
you would indeed get entirely different IPs in the result if you
issue enough queries. This was with BIND 9.3.4-P1, YMMV.
% tcpdump -r tcp.dump -txv udp
reading from file tcp.dump, link-type NULL (BSD loopback)
IP (tos 0x0, ttl 64, id 52075, offset 0, flags [none], length: 62)
localhost.59718 > localhost.domain: [udp sum ok] 61756+ A?
test.example.com. (34)
0x0000: 4500 003e cb6b 0000 4011 b141 7f00 0001
E..>[EMAIL PROTECTED]
0x0010: 7f00 0001 e946 0035 002a db27 f13c 0100 .....F.
5.*.'.<..
0x0020: 0001 0000 0000 0000 0474 6573 7407
6578 .........test.ex
0x0030: 616d 706c 6503 636f 6d00 0001 0001
ample.com.....
IP (tos 0x0, ttl 64, id 52076, offset 0, flags [none], length: 526)
localhost.domain > localhost.59718: [udp sum ok] 61756*| 29/0/0
test.example.com. A 192.168.1.0, test.example.com. A
linksys.pkix.net, test.example.com. A sec.pkix.net, test.example.com.
A prime.pkix.net, test.example.com. A mac.pkix.net, test.example.com.
A rho.pkix.net, test.example.com. A cube.pkix.net, test.example.com.
A 192.168.1.7, test.example.com. A 192.168.1.8, test.example.com. A
192.168.1.9, test.example.com. A 192.168.1.10, test.example.com. A
192.168.1.11, test.example.com. A 192.168.1.12, test.example.com. A
192.168.1.13, test.example.com. A 192.168.1.14, test.example.com. A
192.168.1.15, test.example.com. A 192.168.1.16, test.example.com. A
192.168.1.17, test.example.com. A 192.168.1.18, test.example.com. A
192.168.1.19, test.example.com. A 192.168.1.20, test.example.com. A
192.168.1.21, test.example.com. A 192.168.1.22, test.example.com. A
192.168.1.23, test.example.com. A 192.168.1.24, test.example.com. A
192.168.1.25, test.example.com. A 192.168.1.26, test.example.com. A
192.168.1.27, test.example.com. A 192.168.1.28 (498)
0x0000: 4500 020e cb6c 0000 4011 af70 7f00 0001
[EMAIL PROTECTED]
0x0010: 7f00 0001 0035 e946 01fa 6170 f13c 8780 .....
5.F..ap.<..
0x0020: 0001 001d 0000 0000 0474 6573 7407
6578 .........test.ex
0x0030: 616d 706c 6503 636f 6d00 0001 0001 c00c
ample.com.......
0x0040: 0001 0001 0001 5180 0004 c0a8 0100
c00c ......Q.........
0x0050: 0001 0001 0001 5180 0004 c0a8 0101
c00c ......Q.........
0x0060: 0001 0001 0001 5180 0004 c0a8 0102
c00c ......Q.........
0x0070: 0001 0001 0001 5180 0004 c0a8 0103
c00c ......Q.........
0x0080: 0001 0001 0001 5180 0004 c0a8 0104
c00c ......Q.........
0x0090: 0001 0001 0001 5180 0004 c0a8 0105
c00c ......Q.........
0x00a0: 0001 0001 0001 5180 0004 c0a8 0106
c00c ......Q.........
0x00b0: 0001 0001 0001 5180 0004 c0a8 0107
c00c ......Q.........
0x00c0: 0001 0001 0001 5180 0004 c0a8 0108
c00c ......Q.........
0x00d0: 0001 0001 0001 5180 0004 c0a8 0109
c00c ......Q.........
0x00e0: 0001 0001 0001 5180 0004 c0a8 010a
c00c ......Q.........
0x00f0: 0001 0001 0001 5180 0004 c0a8 010b
c00c ......Q.........
0x0100: 0001 0001 0001 5180 0004 c0a8 010c
c00c ......Q.........
0x0110: 0001 0001 0001 5180 0004 c0a8 010d
c00c ......Q.........
0x0120: 0001 0001 0001 5180 0004 c0a8 010e
c00c ......Q.........
0x0130: 0001 0001 0001 5180 0004 c0a8 010f
c00c ......Q.........
0x0140: 0001 0001 0001 5180 0004 c0a8 0110
c00c ......Q.........
0x0150: 0001 0001 0001 5180 0004 c0a8 0111
c00c ......Q.........
0x0160: 0001 0001 0001 5180 0004 c0a8 0112
c00c ......Q.........
0x0170: 0001 0001 0001 5180 0004 c0a8 0113
c00c ......Q.........
0x0180: 0001 0001 0001 5180 0004 c0a8 0114
c00c ......Q.........
0x0190: 0001 0001 0001 5180 0004 c0a8 0115
c00c ......Q.........
0x01a0: 0001 0001 0001 5180 0004 c0a8 0116
c00c ......Q.........
0x01b0: 0001 0001 0001 5180 0004 c0a8 0117
c00c ......Q.........
0x01c0: 0001 0001 0001 5180 0004 c0a8 0118
c00c ......Q.........
0x01d0: 0001 0001 0001 5180 0004 c0a8 0119
c00c ......Q.........
0x01e0: 0001 0001 0001 5180 0004 c0a8 011a
c00c ......Q.........
0x01f0: 0001 0001 0001 5180 0004 c0a8 011b
c00c ......Q.........
0x0200: 0001 0001 0001 5180 0004 c0a8
011c ......Q.......
[ ...repeat the query several times... ]
IP (tos 0x0, ttl 64, id 52953, offset 0, flags [none], length: 62)
127.0.0.1.65250 > 127.0.0.1.53: [udp sum ok] 43924+ A?
test.example.com. (34)
0x0000: 4500 003e ced9 0000 4011 add3 7f00 0001
E..>[EMAIL PROTECTED]
0x0010: 7f00 0001 fee2 0035 002a 0b34 ab94 0100 .......5.*.
4....
0x0020: 0001 0000 0000 0000 0474 6573 7407
6578 .........test.ex
0x0030: 616d 706c 6503 636f 6d00 0001 0001
ample.com.....
IP (tos 0x0, ttl 64, id 52955, offset 0, flags [none], length: 526)
127.0.0.1.53 > 127.0.0.1.65250: [udp sum ok] 43924*| 29/0/0
test.example.com. A 192.168.1.214, test.example.com. A 192.168.1.215,
test.example.com. A 192.168.1.216, test.example.com. A 192.168.1.217,
test.example.com. A 192.168.1.218, test.example.com. A 192.168.1.219,
test.example.com. A 192.168.1.220, test.example.com. A 192.168.1.221,
test.example.com. A 192.168.1.222, test.example.com. A 192.168.1.223,
test.example.com. A 192.168.1.224, test.example.com. A 192.168.1.225,
test.example.com. A 192.168.1.226, test.example.com. A 192.168.1.227,
test.example.com. A 192.168.1.228, test.example.com. A 192.168.1.229,
test.example.com. A 192.168.1.230, test.example.com. A 192.168.1.231,
test.example.com. A 192.168.1.232, test.example.com. A 192.168.1.233,
test.example.com. A 192.168.1.234, test.example.com. A 192.168.1.235,
test.example.com. A 192.168.1.236, test.example.com. A 192.168.1.237,
test.example.com. A 192.168.1.238, test.example.com. A 192.168.1.239,
test.example.com. A 192.168.1.240, test.example.com. A 192.168.1.241,
test.example.com. A 192.168.1.242 (498)
0x0000: 4500 020e cedb 0000 4011 ac01 7f00 0001
[EMAIL PROTECTED]
0x0010: 7f00 0001 0035 fee2 01fa 793e ab94 8780 .....
5....y>....
0x0020: 0001 001d 0000 0000 0474 6573 7407
6578 .........test.ex
0x0030: 616d 706c 6503 636f 6d00 0001 0001 c00c
ample.com.......
0x0040: 0001 0001 0001 5180 0004 c0a8 01d6
c00c ......Q.........
0x0050: 0001 0001 0001 5180 0004 c0a8 01d7
c00c ......Q.........
0x0060: 0001 0001 0001 5180 0004 c0a8 01d8
c00c ......Q.........
0x0070: 0001 0001 0001 5180 0004 c0a8 01d9
c00c ......Q.........
0x0080: 0001 0001 0001 5180 0004 c0a8 01da
c00c ......Q.........
0x0090: 0001 0001 0001 5180 0004 c0a8 01db
c00c ......Q.........
0x00a0: 0001 0001 0001 5180 0004 c0a8 01dc
c00c ......Q.........
0x00b0: 0001 0001 0001 5180 0004 c0a8 01dd
c00c ......Q.........
0x00c0: 0001 0001 0001 5180 0004 c0a8 01de
c00c ......Q.........
0x00d0: 0001 0001 0001 5180 0004 c0a8 01df
c00c ......Q.........
0x00e0: 0001 0001 0001 5180 0004 c0a8 01e0
c00c ......Q.........
0x00f0: 0001 0001 0001 5180 0004 c0a8 01e1
c00c ......Q.........
0x0100: 0001 0001 0001 5180 0004 c0a8 01e2
c00c ......Q.........
0x0110: 0001 0001 0001 5180 0004 c0a8 01e3
c00c ......Q.........
0x0120: 0001 0001 0001 5180 0004 c0a8 01e4
c00c ......Q.........
0x0130: 0001 0001 0001 5180 0004 c0a8 01e5
c00c ......Q.........
0x0140: 0001 0001 0001 5180 0004 c0a8 01e6
c00c ......Q.........
0x0150: 0001 0001 0001 5180 0004 c0a8 01e7
c00c ......Q.........
0x0160: 0001 0001 0001 5180 0004 c0a8 01e8
c00c ......Q.........
0x0170: 0001 0001 0001 5180 0004 c0a8 01e9
c00c ......Q.........
0x0180: 0001 0001 0001 5180 0004 c0a8 01ea
c00c ......Q.........
0x0190: 0001 0001 0001 5180 0004 c0a8 01eb
c00c ......Q.........
0x01a0: 0001 0001 0001 5180 0004 c0a8 01ec
c00c ......Q.........
0x01b0: 0001 0001 0001 5180 0004 c0a8 01ed
c00c ......Q.........
0x01c0: 0001 0001 0001 5180 0004 c0a8 01ee
c00c ......Q.........
0x01d0: 0001 0001 0001 5180 0004 c0a8 01ef
c00c ......Q.........
0x01e0: 0001 0001 0001 5180 0004 c0a8 01f0
c00c ......Q.........
0x01f0: 0001 0001 0001 5180 0004 c0a8 01f1
c00c ......Q.........
0x0200: 0001 0001 0001 5180 0004 c0a8
01f2 ......Q.......
--
-Chuck
PS: Ignore the fact that I've got reverse DNS entries for pkix.net
for 192.168.1.1 - .7 or so. :-)
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