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*SOLVED* IP ping works, DNS IP ping doesnt work [message #23368]

Fri, 16 November 2007 03:35

oliver
Messages: 5
Registered: November 2007

Junior Member

hi,

i just recognized an intresting thing:

# ping google.com

nothing happens.

# host google.com <public DNS Server IP>
Using domain server:
Name: <public DNS Server IP>
Address: <public DNS Server IP>#53
Aliases:

google.com has address 72.14.207.99
google.com has address 64.233.167.99
google.com has address 64.233.187.99

# ping <public DNS Server IP>

respond

# ping <DNS Hostname of public DNS Server IP>

nothing happens

# route -n

# route -n
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.1.0 0.0.0.0 255.255.255.255 UH 0 0 0 venet0
192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 venet0
0.0.0.0 192.168.1.1 0.0.0.0 UG 0 0 0 venet0

# cat /etc/resolv.conf
nameserver <public DNS Server IP>

All commands has been put in the vps itself. The vps is Debian 64 Bit running on 64 Bit Centos 5 on 2.6.18-ovz028stab047.1-smp

The Hostmachine doesnt have any problems.

In General the vps services cant do an dns lookup.

ssh -v 192.168.1.40
OpenSSH_4.3p2 Debian-9, OpenSSL 0.9.8c 05 Sep 2006
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
debug1: Connecting to 192.168.1.40 [192.168.1.40] port 22.
debug1: Connection established.
debug1: permanently_set_uid: 0/0
debug1: identity file /root/.ssh/identity type -1
debug1: identity file /root/.ssh/id_rsa type -1
debug1: identity file /root/.ssh/id_dsa type -1

The vps is pingable from the outside.
The vps can ping every IP.

I dont really get the problem. If anyone know anything i would be thankfull.

Have a nice day Smile

Greetings
Oliver

[Updated on: Fri, 16 November 2007 16:26] by Moderator

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Re: IP ping works, DNS IP ping doesnt work [message #23373 is a reply to message #23368]

Fri, 16 November 2007 06:30

vaverin
Messages: 708
Registered: September 2005

Senior Member

Hi Oliver,

are you sure that you have set correct nameserver's IP? Could you please check that you have correct response from DNS server?
Could you please try to add some another nameserver to /ets/resolv.conf?

Thank you,
Vasily Averin

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Re: IP ping works, DNS IP ping doesnt work [message #23374 is a reply to message #23373]

Fri, 16 November 2007 06:37

vaverin
Messages: 708
Registered: September 2005

Senior Member

Could you please also check the settings in /etc/nsswitch.conf file?

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Re: IP ping works, DNS IP ping doesnt work [message #23414 is a reply to message #23368]

Fri, 16 November 2007 13:38

oliver
Messages: 5
Registered: November 2007

Junior Member

hi,

thanks so far for the replay.

I am using for example 193.24.208.126

And for nsswitch.conf:

# cat /etc/nsswitch.conf
# /etc/nsswitch.conf
#
# Example configuration of GNU Name Service Switch functionality.
# If you have the `glibc-doc-reference' and `info' packages installed, try:
# `info libc "Name Service Switch"' for information about this file.

passwd: compat
group: compat
shadow: compat

hosts: files dns
networks: files

protocols: db files
services: db files
ethers: db files
rpc: db files

netgroup: nis

# ping google.com

# host google.com 193.24.208.126
Using domain server:
Name: 193.24.208.126
Address: 193.24.208.126#53
Aliases:

google.com has address 72.14.207.99
google.com has address 64.233.167.99
google.com has address 64.233.187.99
google.com mail is handled by 10 smtp4.google.com.
google.com mail is handled by 10 smtp1.google.com.
google.com mail is handled by 10 smtp2.google.com.
google.com mail is handled by 10 smtp3.google.com.

#ping 72.14.207.99
PING 72.14.207.99 (72.14.207.99) 56(84) bytes of data.
64 bytes from 72.14.207.99: icmp_seq=1 ttl=240 time=113 ms
64 bytes from 72.14.207.99: icmp_seq=2 ttl=240 time=113 ms
64 bytes from 72.14.207.99: icmp_seq=3 ttl=240 time=113 ms
64 bytes from 72.14.207.99: icmp_seq=4 ttl=240 time=112 ms

--- 72.14.207.99 ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 2998ms
rtt min/avg/max/mdev = 112.961/113.283/113.619/0.505 ms

Regards

Oliver

[Updated on: Fri, 16 November 2007 13:40]

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Re: IP ping works, DNS IP ping doesnt work [message #23422 is a reply to message #23414]

Fri, 16 November 2007 14:13

vaverin
Messages: 708
Registered: September 2005

Senior Member

let's add "nameserver 4.2.2.4" to your /etc/resolv.conf file.
Then it make sense that the same commands works successfuuly on HN.

Then you can try to trace outgoing packets and responses by using tcpdump:
- inside VE on venet0 interface
- on HN on venet0 interface
- on HN on external interface (i.e eth0)

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Re: IP ping works, DNS IP ping doesnt work [message #23434 is a reply to message #23422]

Fri, 16 November 2007 15:46

oliver
Messages: 5
Registered: November 2007

Junior Member

hi,

# echo nameserver 4.2.2.4 > /etc/resolv.conf
# ping google.com

# host google.com 4.2.2.4
;; connection timed out; no servers could be reached
Segmentation fault
# host google.com 4.2.2.4
;; connection timed out; no servers could be reached
Segmentation fault

At this time i tried on another host server maschine this dns server with success. Then i tried again in the vps:

# host google.com 4.2.2.4
Using domain server:
Name: 4.2.2.4
Address: 4.2.2.4#53
Aliases:

google.com has address 64.233.187.99
google.com has address 64.233.167.99
google.com has address 72.14.207.99
google.com mail is handled by 10 smtp3.google.com.
google.com mail is handled by 10 smtp4.google.com.
google.com mail is handled by 10 smtp1.google.com.
google.com mail is handled by 10 smtp2.google.com.
sv1:/# host google.com 4.2.2.4
Using domain server:
Name: 4.2.2.4
Address: 4.2.2.4#53
Aliases:

google.com has address 64.233.187.99
google.com has address 64.233.167.99
google.com has address 72.14.207.99
google.com mail is handled by 10 smtp2.google.com.
google.com mail is handled by 10 smtp3.google.com.
google.com mail is handled by 10 smtp4.google.com.
google.com mail is handled by 10 smtp1.google.com.

# ping google.com

But also here nothing happens.

On Host machine:
# tcpdump -i venet0 | grep 192.168.1.40

Nothing comes along when i do ping or something

# tcpdump -i eth0 | grep 192.168.1.40

16:41:29.164202 IP 81.210.246.158 > 192.168.1.40: ICMP echo request, id 48110, seq 2048, length 40
16:41:29.164244 IP 192.168.1.40 > 81.210.246.158: ICMP echo reply, id 48110, seq 2048, length 40
16:41:30.164393 IP 81.210.246.158 > 192.168.1.40: ICMP echo request, id 48110, seq 2304, length 40
16:41:30.164421 IP 192.168.1.40 > 81.210.246.158: ICMP echo reply, id 48110, seq 2304, length 40

When i ping the vps from outside network

tcpdump on vps is not working because tcpdump its not available.
I will begin to create a complete new raw vps because it was working once as i remember.

Greetings
Oliver

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Re: IP ping works, DNS IP ping doesnt work [message #23439 is a reply to message #23368]

Fri, 16 November 2007 16:18

oliver
Messages: 5
Registered: November 2007

Junior Member

hi,

OK i got it.

cat /proc/user_beancounters

showed a hit of limit at:

othersockbuf

of 465 failcnt.

I raised the limit.

Then i got 21 failcnt.

Then i raised the barrier and now its working.

When i had failcnt of 21 i was able to ping. But the apache2 webserver didnt start.

Now barrier AND limit is high enough that no failcnt is acountet.

So the case can be closed. Thanks for the help anyway Smile

Greetings
Oliver

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