netlook

Well-Known Member
Mar 25, 2004
335
0
166
Hi,

I have strange problem on fresh CentOS/cPanel server.

From time to time network simply dies. I was SSH into server, then I noticed that I can not view any webpage from it.

I did netstat -n but it only show somethink like this:

Code:
Active UNIX domain sockets (w/o servers)
Proto RefCnt Flags       Type       State         I-Node Path
unix  13     [ ]         DGRAM                    6272   /dev/log
unix  2      [ ]         DGRAM                    11091  @/var/run/hal/hotplug_socket
unix  2      [ ]         DGRAM                    3466   @udevd
unix  2      [ ]         DGRAM                    137333
unix  2      [ ]         DGRAM                    130898
unix  2      [ ]         STREAM     CONNECTED     123293
unix  3      [ ]         STREAM     CONNECTED     11090  /var/run/dbus/system_bus_socket
unix  3      [ ]         STREAM     CONNECTED     11089
unix  3      [ ]         STREAM     CONNECTED     11013
unix  3      [ ]         STREAM     CONNECTED     11012
unix  2      [ ]         DGRAM                    10842
unix  2      [ ]         DGRAM                    9749
unix  2      [ ]         DGRAM                    8360
unix  2      [ ]         DGRAM                    8343
unix  2      [ ]         DGRAM                    8320
unix  2      [ ]         DGRAM                    8301
unix  2      [ ]         DGRAM                    8079
unix  2      [ ]         DGRAM                    6484
unix  2      [ ]         DGRAM                    6353
unix  2      [ ]         DGRAM                    6280
Then I did:

service network restart

but it did not help. I need to reboot server.

What it could be? Is this a problem with ifcfg-eth0 - I have somethink like this on problematic server:

Code:
DEVICE=eth0
BOOTPROTO=dhcp
HWADDR=00:13:D3:E4:EE:ED
ONBOOT=yes
TYPE=Ethernet
When I start my server I get this in /var/log/messages:

Code:
network: Setting network parameters:  succeeded
network: Bringing up loopback interface:  succeeded
ifup:
ifup: Determining IP information for eth0...
dhclient: DHCPREQUEST on eth0 to 255.255.255.255 port 67
dhclient: DHCPACK from [MY_MAIN_IP]
NET: /sbin/dhclient-script : updated /etc/resolv.conf
dhclient: bound to [MY_MAIN_IP] -- renewal in 70990 seconds.
ifup:  done.
NET: /etc/sysconfig/network-scripts/ifup-post : updated /etc/resolv.conf
network: Bringing up interface eth0:  succeeded
filelimits: Increasing file system limits succeeded
ipaliases: Bringing up eth0:1 succeeded
ipaliases: Routing 88.198.109.138 succeeded
ipaliases: Bringing up eth0:2 succeeded
ipaliases: Routing 88.198.109.139 succeeded
ipaliases: Bringing up eth0:3 succeeded
ipaliases: Routing 88.198.109.140 succeeded
ipaliases: Bringing up eth0:4 succeeded
ipaliases: Routing 88.198.109.141 succeeded
ipaliases: Bringing up eth0:5 succeeded
ipaliases: Routing 88.198.109.142 succeeded
Can anyone help me with this?
 
Last edited:

chirpy

Well-Known Member
Verifed Vendor
Jun 15, 2002
13,465
30
473
Go on, have a guess
Is it only apache that you have problems accessing or the whole server? IF it's just apache then you could be hitting MaxClients (check the error_log), if it's everything, check the output of ifconfig and see if there are any errors logged against the NIC. If there are it could be a faulty NIC/cable/connection or local network problems.
 

jsilvestre

Member
Jul 7, 2005
24
0
151
Problem with network

Dear netlook,

did you have eth0 with dhcp?
 

chirpy

Well-Known Member
Verifed Vendor
Jun 15, 2002
13,465
30
473
Go on, have a guess
That output looks fine. Are you able to SSH into the server when this happens or are you using a remote console? If the latter, and you shutdown iptables (APF) can you ping an external IP address from the server? If you can't then it would suggest network problems to me.
 

netlook

Well-Known Member
Mar 25, 2004
335
0
166
Hi Chirpy!

Thanks for reply.

This is output of my *ifconfig*:

Code:
eth0      Link encap:Ethernet  HWaddr 00:13:D3:E4:EE:ED
          inet addr:[MAIN-IP-ADDRESS]  Bcast:[MAIN-IP-ADDRESS]  Mask:255.255.255.224
          inet6 addr: fe80::213:d3ff:fee4:eeed/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:1743494 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1149144 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:1861687602 (1.7 GiB)  TX bytes:530993292 (506.3 MiB)
          Interrupt:177 Base address:0x6000

eth0:1    Link encap:Ethernet  HWaddr 00:13:D3:E4:EE:ED
          inet addr:[ADDITIONAL-IP-1]  Bcast:[ADDITIONAL-IP-LAST]  Mask:255.255.255.248
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          Interrupt:177 Base address:0x6000

eth0:2    Link encap:Ethernet  HWaddr 00:13:D3:E4:EE:ED
          inet addr:[ADDITIONAL-IP-2]  Bcast:[ADDITIONAL-IP-LAST]  Mask:255.255.255.248
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          Interrupt:177 Base address:0x6000

eth0:3    Link encap:Ethernet  HWaddr 00:13:D3:E4:EE:ED
          inet addr:[ADDITIONAL-IP-3]  Bcast:[ADDITIONAL-IP-LAST]  Mask:255.255.255.248
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          Interrupt:177 Base address:0x6000

eth0:4    Link encap:Ethernet  HWaddr 00:13:D3:E4:EE:ED
          inet addr:[ADDITIONAL-IP-4]  Bcast:[ADDITIONAL-IP-LAST]  Mask:255.255.255.248
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          Interrupt:177 Base address:0x6000

eth0:5    Link encap:Ethernet  HWaddr 00:13:D3:E4:EE:ED
          inet addr:[ADDITIONAL-IP-5]  Bcast:[ADDITIONAL-IP-LAST] Mask:255.255.255.248
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          Interrupt:177 Base address:0x6000

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:7313 errors:0 dropped:0 overruns:0 frame:0
          TX packets:7313 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:2433235 (2.3 MiB)  TX bytes:2433235 (2.3 MiB)
It is not only Apache, it is also POP3 or SMTP, I can't access cPanel too. I tried to shutdown APF/restart APF during problems, but it did not help.
 

netlook

Well-Known Member
Mar 25, 2004
335
0
166
That output looks fine. Are you able to SSH into the server when this happens or are you using a remote console? If the latter, and you shutdown iptables (APF) can you ping an external IP address from the server? If you can't then it would suggest network problems to me.

It happend and I was ssh into the server during the problems (I logged before it happen). I was able to ping external IPs from the server but I cant access any service on the server from 2 different internet connections.
 

jsilvestre

Member
Jul 7, 2005
24
0
151
Problem with network

Try use netconfig to reconfigure IP address again.
 

AlexandreVeezon

Well-Known Member
Dec 9, 2005
103
2
168
/br/sc/rionegrinho
cPanel Access Level
Root Administrator
Hi!
The same happen with one of my machines.
But in my case, the network dies just when the link goes down. Everytime we need to restart the link, ifconfig downs other IPs, remaining up only the main IP address.. So i have to up all the IPs again.. ifconfig eth0:1, eth0:2, eth0:3...
Pretty strange :confused:

I'm searching for details in logs you have said in this thread...
 

AlexandreVeezon

Well-Known Member
Dec 9, 2005
103
2
168
/br/sc/rionegrinho
cPanel Access Level
Root Administrator
Well

I see one diference between 2 machines:
In problematic one, I have NetworkManager on in chkconfig.
In good one, the NetworkManager is off.
It could be my problem?

Look at this:

Problematic Machine
Code:
[email protected] [/var/log]# chkconfig --list | grep -i net
NetworkManager  0:off     1:off     2:off     3:on      4:off     5:off     6:off
netplugd        0:off     1:off     2:off     3:off     4:off     5:off     6:off
network         0:off     1:off     2:on      3:on      4:on      5:on      6:off
netdump         0:off     1:off     2:off     3:off     4:off     5:off     6:off
netfs           0:off     1:off     2:off     3:on      4:on      5:on      6:off
xinetd          0:off     1:off     2:off     3:on      4:on      5:on      6:off
servces based on xinetd:
        krb5-telnet:    off
Good Machine
Code:
[email protected] [/]# chkconfig --list | grep -i net
NetworkManager  0:off     1:off     2:off     3:off     4:off     5:off     6:off
netplugd        0:off     1:off     2:off     3:off     4:off     5:off     6:off
network         0:off     1:off     2:on      3:on      4:on      5:on      6:off
netdump         0:off     1:off     2:off     3:off     4:off     5:off     6:off
netfs           0:off     1:off     2:off     3:on      4:on      5:on      6:off
xinetd          0:off     1:off     2:off     3:on      4:on      5:on      6:off
services based on xinetd:
        krb5-telnet:    off
In additional, I run a test. I first unplugged the network cable from machine and plugged again. When the cable was off, all IPs goes down (except main IP). When the cable was put again, the IPs was still down, so I has to run service ipaliases restart. See the log:
Code:
Jun  5 10:25:37 server kernel: eth0: link down
Jun  5 10:25:40 server NetworkManager: AUTO: Best wired device = (null)
Jun  5 10:25:40 server NetworkManager: AUTO: Best wireless device = (null)  (null)
Jun  5 10:25:40 server NetworkManager:     SWITCH: best device changed
Jun  5 10:25:46 server kernel: eth0: link up, 100Mbps, full-duplex, lpa 0x41E1
Jun  5 10:25:50 server NetworkManager: AUTO: Best wired device = eth0
Jun  5 10:25:50 server NetworkManager: AUTO: Best wireless device = (null)  (null)
Jun  5 10:25:50 server NetworkManager:     SWITCH: best device changed
Jun  5 10:25:50 server NetworkManager: nm_state_modification_monitor(): beginning activation for device 'eth0'
Jun  5 10:25:51 server named[3059]: client 72.30.58.113#54537: error sending response: network unreachable
Jun  5 10:25:52 server named[3059]: client 72.30.58.113#53868: error sending response: network unreachable
Jun  5 10:25:53 server NetworkManager: nm_state_modification_monitor() activated device eth0
Jun  5 10:26:19 server ifconfig: SIOCSIFFLAGS: Unable to access required address
Jun  5 10:26:19 server ipaliases: Shutting down eth0:1 failed
Jun  5 10:26:19 server route: SIOCDELRT: Device does not exists
Jun  5 10:26:19 server ipaliases: UnRouting 201.47.86.17 failed
Jun  5 10:26:19 server ifconfig: SIOCSIFFLAGS: Unable to access required address
Jun  5 10:26:19 server ipaliases: Shutting down eth0:2 failed
Jun  5 10:26:19 server route: SIOCDELRT: Device does not exists
Jun  5 10:26:19 server ipaliases: UnRouting 201.47.86.18 failed
Jun  5 10:26:19 server ifconfig: SIOCSIFFLAGS: Unable to access required address
Jun  5 10:26:19 server ipaliases: Shutting down eth0:3 failed
Jun  5 10:26:19 server route: SIOCDELRT: Device does not exists
Jun  5 10:26:19 server ipaliases: UnRouting 201.47.86.19 failed
Jun  5 10:26:19 server ifconfig: SIOCSIFFLAGS: Unable to access required address
Jun  5 10:26:20 server ipaliases: Shutting down eth0:4 failed
Jun  5 10:26:21 server route: SIOCDELRT: Device does not exists
Jun  5 10:26:23 server ipaliases: UnRouting 201.47.86.20 failed
Jun  5 10:26:25 server ifconfig: SIOCSIFFLAGS: Unable to access required address
Jun  5 10:26:25 server ipaliases: Shutting down eth0:5 failed
Jun  5 10:26:25 server route: SIOCDELRT: Device does not exists
Jun  5 10:26:26 server ipaliases: UnRouting 201.47.86.21 failed
Jun  5 10:26:27 server ifconfig: SIOCGIFADDR: Unable to access required address
Jun  5 10:26:27 server ifconfig: SIOCSIFBROADCAST: Unable to access required address
Jun  5 10:26:28 server ifconfig: SIOCSIFBRDADDR: Unable to access required address
Jun  5 10:26:28 server ifconfig: SIOCSIFFLAGS: Unable to access required address
Jun  5 10:26:28 server ipaliases: Bringing up eth0:1 failed
Jun  5 10:26:30 server route: SIOCADDRT: Device does not exists
Jun  5 10:26:30 server ipaliases: Routing 201.47.86.17 failed
Jun  5 10:26:30 server ipaliases: Bringing up eth0:2 succeeded
Jun  5 10:26:30 server ipaliases: Routing 201.47.86.18 succeeded
Jun  5 10:26:30 server ipaliases: Bringing up eth0:3 succeeded
Jun  5 10:26:30 server ipaliases: Routing 201.47.86.19 succeeded
Jun  5 10:26:31 server ipaliases: Bringing up eth0:4 succeeded
Jun  5 10:26:31 server ipaliases: Routing 201.47.86.20 succeeded
Jun  5 10:26:31 server ipaliases: Bringing up eth0:5 succeeded
Jun  5 10:26:32 server ipaliases: Routing 201.47.86.21 succeeded
 
Last edited:

AndyReed

Well-Known Member
PartnerNOC
May 29, 2004
2,221
4
193
Minneapolis, MN
Sorry to bother you, but nobody knows what is the NetworkManager in my issue?
I don't know if I can turn this off, what to install..
Any help will be appreciated.
I suggest you contact your host or your network provider and ask them to test your VLan or VPN. If no problem found, it might be a hardware problem and you might want to replace your server ethernet card.