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Old 10-31-2014, 10:13 AM   #1
jlcostinha
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Registered: Oct 2014
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Centos 6.5 DNS problem ( dig reports no servers could be reached.. from internet.)

hi all

i had centos 6.1 with DNS service working for years without any problem.Few days ago, had to replace hard disk and decided to upgrade to CENTOS 6.5! using same configuration of zone files/named.conf i am having wierd problem i can't seem able to overcame it. i could appreciate your assistance.

my ISP provider reports when query NS :
Quote:
DnsException: Error #2; Servidor inacessível; Server unreachable; 194.79.75.138
****++++****++++****
; <<>> DiG 9.7.0-P2 <<>> @194.79.75.138 m3t.pt NS +norecurse
; (1 server found)
;; global options: +cmd
;; connection timed out; no servers could be reached
****++++****++++****
Local on my server i get:
Quote:
[root@firewall ~]# dig @194.79.75.138 m3t.pt

; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.23.rc1.el6_5.1 <<>> @194.79.75.138 m3t.pt
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 28528
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 2

;; QUESTION SECTION:
;m3t.pt. IN A

;; ANSWER SECTION:
m3t.pt. 10800 IN A 194.79.75.138

;; AUTHORITY SECTION:
m3t.pt. 10800 IN NS ns.m3t.pt.
m3t.pt. 10800 IN NS ns.halla.pt.

;; ADDITIONAL SECTION:
ns.m3t.pt. 10800 IN A 194.79.75.138
ns.halla.pt. 86400 IN A 212.18.172.26

;; Query time: 1 msec
;; SERVER: 194.79.75.138#53(194.79.75.138)
;; WHEN: Fri Oct 31 14:51:16 2014
;; MSG SIZE rcvd: 112

[root@firewall ~]#
[root@firewall ~]#
[root@firewall ~]# dig @194.79.75.138 m3t.pt

; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.23.rc1.el6_5.1 <<>> @194.79.75.138 m3t.pt
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 50050
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 2

;; QUESTION SECTION:
;m3t.pt. IN A

;; ANSWER SECTION:
m3t.pt. 10800 IN A 194.79.75.138

;; AUTHORITY SECTION:
m3t.pt. 10800 IN NS ns.m3t.pt.
m3t.pt. 10800 IN NS ns.halla.pt.

;; ADDITIONAL SECTION:
ns.m3t.pt. 10800 IN A 194.79.75.138
ns.halla.pt. 86400 IN A 212.18.172.26

;; Query time: 0 msec
;; SERVER: 194.79.75.138#53(194.79.75.138)
;; WHEN: Fri Oct 31 15:01:33 2014
;; MSG SIZE rcvd: 112
outside from another server over the internet:
Quote:
# dig @194.79.75.138 m3t.pt NS


; <<>> DiG 9.3.6-P1-RedHat-9.3.6-20.P1.el5_8.6 <<>> @194.79.75.138 m3t.pt NS
; (1 server found)
;; global options: printcmd
;; connection timed out; no servers could be reached
my files are as follows:
named.conf
Quote:
[root@firewall etc]# cat named.conf
//
// named.conf
//
// Provided by Red Hat bind package to configure the ISC BIND named(8) DNS
// server as a caching only nameserver (as a localhost DNS resolver only).
//
// See /usr/share/doc/bind*/sample/ for example named configuration files.
//

options {
listen-on port 53 { any; };
listen-on-v6 port 53 { ::1; };
directory "/var/named";
dump-file "/var/named/data/cache_dump.db";
statistics-file "/var/named/data/named_stats.txt";
memstatistics-file "/var/named/data/named_mem_stats.txt";

// allow-query { any; };
// allow-query-cache { any; };
// recursion no;

allow-recursion { any; };
allow-query { any; };
allow-query-cache { any; };

dnssec-enable no;
dnssec-validation no;
dnssec-lookaside auto;

/* Path to ISC DLV key */
bindkeys-file "/etc/named.iscdlv.key";

managed-keys-directory "/var/named/dynamic";
};

logging {
channel default_debug {
file "data/named.run";
severity dynamic;
};
};

zone "." IN {
type hint;
file "named.ca";
};

include "/etc/named.rfc1912.zones";
include "/etc/named.root.key";
include "/etc/named.conf.local";
include "/etc/rndc.key";
named.conf.local
Quote:
zone "m3t.pt" {
type master;
file "/var/named/m3t.pt.zone";
allow-transfer { 69.72.158.226;212.18.172.26;209.126.159.118; };
};
zone "75.79.194.in-addr.arpa" {
type master;
file "/var/named/75.79.194.in-addr.arpa.zone";
allow-transfer { 69.72.158.226;212.18.172.26;209.126.159.118; };
};
zone "1.168.192.in-addr.arpa" {
type master;
file "/var/named/1.168.192.in-addr.arpa.zone";
};

zone "halla.pt" {
type slave;
file "halla.pt.zone";
allow-transfer { 212.18.172.26; };
masters { 212.18.172.26; };
};
zone "172.18.212.in-addr.arpa" {
type slave;
file "172.18.212.in-addr.arpa.zone";
allow-transfer { 212.18.172.26; };
masters { 212.18.172.26; };
};
resolv.conf
Quote:
search m3t.pt
nameserver 192.168.1.253
nameserver 195.23.129.126
nameserver 194.79.69.222
what i have done so far:

-checked router! server is on DMZ zone and firewall is disabled.
i can telnet server on port 53.
- disabled SElinux / iptables
-tried several zone configurations without success.

results i dont understand:

when i run dig ( from internet on an outside server )
Quote:
dig @194.79.75.138 ns.m3t.pt NS

; <<>> DiG 9.3.6-P1-RedHat-9.3.6-20.P1.el5_8.6 <<>> @194.79.75.138 ns.m3t.pt NS
; (1 server found)
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 7516
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0

;; QUESTION SECTION:
;ns.m3t.pt. IN NS

;; AUTHORITY SECTION:
m3t.pt. 3600 IN SOA ns.m3t.pt. root.m3t.pt. 31 10800 3600 604800 3600

;; Query time: 27 msec
;; SERVER: 194.79.75.138#53(194.79.75.138)
;; WHEN: Fri Oct 31 15:09:56 2014
;; MSG SIZE rcvd: 68
i would appreciate some fresh insights on what is the problem.

thanks in advance.

Jorge
Last edited by jlcostinha; 11-01-2014 at 03:37 AM.
 
Old 11-01-2014, 04:35 AM   #2
bathory
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Hi,

From here:
Code:
dig @194.79.75.138 m3t.pt NS

; <<>> DiG 9.10.1 <<>> @194.79.75.138 m3t.pt NS
; (1 server found)
;; global options: +cmd
;; connection timed out; no servers could be reached
Code:
dig @194.79.75.138 m3t.pt NS +tcp

; <<>> DiG 9.10.1 <<>> @194.79.75.138 m3t.pt NS +tcp
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 31863
;; flags: qr aa rd; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 2
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;m3t.pt.                                IN      NS

;; ANSWER SECTION:
m3t.pt.                 10800   IN      NS      ns.halla.pt.
m3t.pt.                 10800   IN      NS      ns.m3t.pt.

;; ADDITIONAL SECTION:
ns.m3t.pt.              10800   IN      A       194.79.75.138

;; Query time: 141 msec
;; SERVER: 194.79.75.138#53(194.79.75.138)
;; WHEN: Sat Nov 01 11:16:29 EET 2014
;; MSG SIZE  rcvd: 91
And
Code:
dig @194.79.75.138 m3t.pt

; <<>> DiG 9.10.1 <<>> @194.79.75.138 m3t.pt
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 27425
;; flags: qr aa rd; QUERY: 1, ANSWER: 2, AUTHORITY: 2, ADDITIONAL: 3
;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;m3t.pt.                                IN      A

;; ANSWER SECTION:
m3t.pt.                 10800   IN      A       194.79.75.138
m3t.pt.                 10800   IN      A       212.18.172.26

;; AUTHORITY SECTION:
m3t.pt.                 10800   IN      NS      ns.halla.pt.
m3t.pt.                 10800   IN      NS      ns.m3t.pt.

;; ADDITIONAL SECTION:
ns.m3t.pt.              10800   IN      A       194.79.75.138
ns.halla.pt.            86400   IN      A       212.18.172.26

;; Query time: 140 msec
;; SERVER: 194.79.75.138#53(194.79.75.138)
;; WHEN: Sat Nov 01 11:16:57 EET 2014
;; MSG SIZE  rcvd: 139
1st and 3rd queries use UDP, while the 2nd uses TCP
Since the last 2 work while the 1st doesn't, I guess there is a router that drops fragmented UDP packets.
Could also be a firewall, but you said you've disable it.

Regards
 
Old 11-01-2014, 09:45 AM   #3
jlcostinha
LQ Newbie
 
Registered: Oct 2014
Posts: 7

Original Poster
Rep: Reputation: Disabled
thank you for answer!

i was able to check UDP listening on port 53 over the internet.

from another server over the internet:
Quote:
nc -vzu 194.79.73.138 53
Connection to 194.79.73.138 53 port [udp/domain] succeeded!
i belived the router is working good.
-----

dig, but instead of domain(m3t.pt) i use ns.m3t.pt :
Quote:
dig @194.79.75.138 ns.m3t.pt NS

; <<>> DiG 9.3.6-P1-RedHat-9.3.6-20.P1.el5_8.6 <<>> @194.79.75.138 ns.m3t.pt NS
; (1 server found)
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 23571
;; flags: qr aa rd; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 0

;; QUESTION SECTION:
;ns.m3t.pt. IN NS

;; AUTHORITY SECTION:
m3t.pt. 3600 IN SOA ns.m3t.pt. root.m3t.pt. 32 10800 3600 604800 3600

;; Query time: 32 msec
;; SERVER: 194.79.75.138#53(194.79.75.138)
;; WHEN: Sat Nov 1 14:40:22 2014
;; MSG SIZE rcvd: 68
otherwise it doesnt reach:
Quote:
dig @194.79.75.138 m3t.pt NS

; <<>> DiG 9.3.6-P1-RedHat-9.3.6-20.P1.el5_8.6 <<>> @194.79.75.138 m3t.pt NS
; (1 server found)
;; global options: printcmd
;; connection timed out; no servers could be reached
i am running out of ideas...
 
Old 11-01-2014, 12:06 PM   #4
bathory
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Location: Piraeus
Distribution: Slackware
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Quote:
i was able to check UDP listening on port 53 over the internet.

from another server over the internet:
Quote:
nc -vzu 194.79.73.138 53
Connection to 194.79.73.138 53 port [udp/domain] succeeded!
i belived the router is working good.
You cannot tell if it drops fragmented UDP packets though. Queries for A, MX RRs work, while for NS, SOA don't
Add the following in named.conf (outside of the options clause):
Code:
server 0.0.0.0/0 {
       edns no;
};
and see if it helps.
 
Old 11-03-2014, 05:13 AM   #5
jlcostinha
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Registered: Oct 2014
Posts: 7

Original Poster
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connection timed out; no servers could be reached

it doesn't work.
 
Old 11-03-2014, 12:14 PM   #6
bathory
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Quote:
Originally Posted by jlcostinha View Post
connection timed out; no servers could be reached

it doesn't work.
I'm out of ideas. If possible try a different router and see what happens.
You can use tcpdump and/or wireshark to see what happens to these packets when looking up NS records
 
Old 11-05-2014, 09:55 AM   #7
jlcostinha
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Registered: Oct 2014
Posts: 7

Original Poster
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problem fixed!

replaced the router and voila. queries were answered...

i am going to downgrade router firmware, i remember i upgraded a year ago.

bathory, thanks a lot for your help!

Jorge
 
Old 11-06-2014, 01:55 AM   #8
bathory
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Registered: Jun 2004
Location: Piraeus
Distribution: Slackware
Posts: 13,194
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Cool!
You may mark the thread "SOLVED" using the thread tools on top of the page.

Cheers
 
Old 11-06-2014, 03:45 AM   #9
jlcostinha
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Registered: Oct 2014
Posts: 7

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just to finish

Router was a drytec 2830 and the firmware was broken.

Found the someone with the same problemas here:
http://forums.whirlpool.net.au/archive/1674673

b4 downgrade, i decided to upgrade firmware and solve the problem.

Again, thanks!

Jorge
 
  


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