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The outgoing "[1au]" queries aren't getting a response. In tcpdump's
display format, I believe "[1au]" means 1 record in the Additional
Section. This would undoubtedly be an OPT record for EDNS0 negotiation.<br>
<br>
I'm having no problems querying those same nameservers with EDNS0 by
the way.<br>
<br>
What you show would, I think, be the expected results of a
recently-restarted nameserver on a network infrastructure that was
dropping EDNS0 packets. Once named "learns" that particular nameservers
don't support EDNS0, however, I believe it would stop trying to use
EDNS0 with them, at least for a while (in case it was just a temporary
problem), so I don't think this would be a persistent issue.<br>
<br>
This is not to say you shouldn't get to the root cause, but I doubt it
actually causes real outages. EDNS0 support was added to BIND with full
knowledge that not all network infrastructures were going to support it
right away...<br>
<br>
I believe +dnssec also turns on EDNS0 unconditionally, so your failures
with +dnssec queries are consistent with my hypothesis.<br>
<br>
- Kevin<br>
<br>
On 6/18/2010 10:20 PM, Rok Potočnik wrote:
<blockquote cite="mid:4C1C2988.4090606@rula.net" type="cite">I'm using
bind 9.7.0-p2 as an authoritive/caching server on a couple of servers
and lately I'm noticing that we're having problems resolving domains
under *.domaincontrol.com servers. The query itself is sent out (as the
tcpdump output down below shows) but only a couple of replies get back.
In case I do a manual lookup using dig, the replies get back every
time. Any ideas on where to look the problem?
<br>
<br>
---
<br>
# tcpdump -nvs0 -ieth1 'host 208.109.255.17 or host 216.69.185.17'
<br>
tcpdump: listening on eth1, link-type EN10MB (Ethernet), capture size
65535 bytes
<br>
04:06:00.189351 IP (tos 0x0, ttl 64, id 5848, offset 0, flags [none],
length: 83) 11.22.33.44.5520 > 216.69.185.17.53: [bad udp cksum
8d70!] 2246 A? ns2.treasurecoasthandymanservices.com. (55)
<br>
04:06:00.230958 IP (tos 0x0, ttl 51, id 0, offset 0, flags [DF],
length: 151) 216.69.185.17.53 > 11.22.33.44.5520: [udp sum ok]
2246*- 1/2/0 ns2.treasurecoasthandymanservices.com. A 184.73.42.183
(123)
<br>
04:06:00.305217 IP (tos 0x0, ttl 64, id 58705, offset 0, flags [none],
length: 80) 11.22.33.44.20025 > 208.109.255.17.53: [bad udp cksum
d552!] 34314% [1au] MX? replacementservices.com. (52)
<br>
04:06:00.360333 IP (tos 0x0, ttl 64, id 5849, offset 0, flags [none],
length: 94) 11.22.33.44.29996 > 216.69.185.17.53: [bad udp cksum
8096!] 62171% [1au] A? ns1.treasurecoasthandymanservices.com. (66)
<br>
04:06:00.360389 IP (tos 0x0, ttl 64, id 5850, offset 0, flags [none],
length: 94) 11.22.33.44.41105 > 216.69.185.17.53: [bad udp cksum
622a!] 13204% [1au] A? ns2.treasurecoasthandymanservices.com. (66)
<br>
04:06:00.360420 IP (tos 0x0, ttl 64, id 5851, offset 0, flags [none],
length: 94) 11.22.33.44.44750 > 216.69.185.17.53: [bad udp cksum
3cf3!] 16765% [1au] AAAA? ns1.treasurecoasthandymanservices.com. (66)
<br>
04:06:00.360483 IP (tos 0x0, ttl 64, id 5852, offset 0, flags [none],
length: 94) 11.22.33.44.60483 > 216.69.185.17.53: [bad udp cksum
8d37!] 49078% [1au] AAAA? ns2.treasurecoasthandymanservices.com. (66)
<br>
04:06:00.539000 IP (tos 0x0, ttl 64, id 5853, offset 0, flags [none],
length: 83) 11.22.33.44.40187 > 216.69.185.17.53: [bad udp cksum
9261!] 36950 A? ns1.treasurecoasthandymanservices.com. (55)
<br>
04:06:00.572696 IP (tos 0x0, ttl 51, id 0, offset 0, flags [DF],
length: 151) 216.69.185.17.53 > 11.22.33.44.40187: [udp sum ok]
36950*- 1/2/0 ns1.treasurecoasthandymanservices.com. A 184.73.99.89
(123)
<br>
04:06:02.619261 IP (tos 0x0, ttl 64, id 58706, offset 0, flags [none],
length: 80) 11.22.33.44.31171 > 208.109.255.17.53: [bad udp cksum
8e06!] 46279% [1au] MX? replacementservices.com. (52)
<br>
04:06:04.389211 IP (tos 0x0, ttl 64, id 58707, offset 0, flags [none],
length: 94) 11.22.33.44.17162 > 208.109.255.17.53: [bad udp cksum
3baf!] 29937% [1au] AAAA? ns2.treasurecoasthandymanservices.com. (66)
<br>
04:06:04.414944 IP (tos 0x0, ttl 64, id 58708, offset 0, flags [none],
length: 94) 11.22.33.44.17486 > 208.109.255.17.53: [bad udp cksum
650e!] 12165% [1au] A? ns1.treasurecoasthandymanservices.com. (66)
<br>
04:06:04.512114 IP (tos 0x0, ttl 64, id 58709, offset 0, flags [none],
length: 94) 11.22.33.44.11845 > 208.109.255.17.53: [bad udp cksum
2460!] 62413% [1au] A? ns2.treasurecoasthandymanservices.com. (66)
<br>
04:06:04.551371 IP (tos 0x0, ttl 64, id 58710, offset 0, flags [none],
length: 94) 11.22.33.44.62132 > 208.109.255.17.53: [bad udp cksum
8e91!] 58100% [1au] AAAA? ns1.treasurecoasthandymanservices.com. (66)
<br>
04:06:06.594682 IP (tos 0x0, ttl 64, id 5854, offset 0, flags [none],
length: 80) 11.22.33.44.29685 > 216.69.185.17.53: [bad udp cksum
6135!] 2067% [1au] MX? replacementservices.com. (52)
<br>
04:06:08.631924 IP (tos 0x0, ttl 64, id 5855, offset 0, flags [none],
length: 69) 11.22.33.44.59535 > 216.69.185.17.53: [bad udp cksum
4a0a!] 16619 MX? replacementservices.com. (41)
<br>
04:06:08.665270 IP (tos 0x0, ttl 51, id 0, offset 0, flags [DF],
length: 180) 216.69.185.17.53 > 11.22.33.44.59535: [udp sum ok]
16619*- 2/2/0 replacementservices.com. MX server24.appriver.com. 10,
replacementservices.com. MX server25.appriver.com. 20 (152)
<br>
04:06:10.664542 IP (tos 0x0, ttl 64, id 5856, offset 0, flags [none],
length: 94) 11.22.33.44.27072 > 216.69.185.17.53: [bad udp cksum
ddc6!] 49385% [1au] AAAA? ns2.treasurecoasthandymanservices.com. (66)
<br>
04:06:10.703845 IP (tos 0x0, ttl 64, id 5857, offset 0, flags [none],
length: 94) 11.22.33.44.14627 > 216.69.185.17.53: [bad udp cksum
b1c6!] 3252% [1au] A? ns1.treasurecoasthandymanservices.com. (66)
<br>
04:06:10.804055 IP (tos 0x0, ttl 64, id 5858, offset 0, flags [none],
length: 94) 11.22.33.44.1134 > 216.69.185.17.53: [bad udp cksum
fbb6!] 20766% [1au] A? ns2.treasurecoasthandymanservices.com. (66)
<br>
04:06:10.841086 IP (tos 0x0, ttl 64, id 5859, offset 0, flags [none],
length: 94) 11.22.33.44.12098 > 216.69.185.17.53: [bad udp cksum
35bf!] 785% [1au] AAAA? ns1.treasurecoasthandymanservices.com. (66)
<br>
04:06:11.251709 IP (tos 0x0, ttl 64, id 58711, offset 0, flags [none],
length: 80) 11.22.33.44.40730 > 208.109.255.17.53: [bad udp cksum
5eae!] 59295% [1au] MX? replacementservices.com. (52)
<br>
---
<br>
<br>
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