if i connect the internet the whole local network internet will be down

pandy669@gmail.com · 04-24-2015, 08:14 AM

My problem is when i connected to the internet the internet is not connecting .
It will make down the whole network internet connection.
when i plug the ethernet cable to my centos 6.6 pc the whole network cannot access the internet.internet will down to whole network .but can be ping with my system but no internet connection.

Before a week i had beed using my system without any problem.
from a last 4 days this problem is happening.
I have given the configuration details of my system
[root@dhcppc0 Desktop]# ip a

Code:

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN 
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
    link/ether 4c:72:b9:21:ba:e4 brd ff:ff:ff:ff:ff:ff
    inet 192.168.5.15/24 brd 192.168.5.255 scope global eth0
    inet6 fe80::4e72:b9ff:fe21:bae4/64 scope link 
       valid_lft forever preferred_lft forever

[root@dhcppc0 Desktop]# ip route

Code:

192.168.5.0/24 dev eth0  proto kernel  scope link  src 192.168.5.15 
169.254.0.0/16 dev eth0  scope link  metric 1002 
default via 192.168.5.2 dev eth0

[root@dhcppc0 Desktop]# ping -I eth0 169.254.0.0

Code:

PING 169.254.0.0 (169.254.0.0) from 192.168.5.15 eth0: 56(84) bytes of data.
From 192.168.5.15 icmp_seq=2 Destination Host Unreachable
From 192.168.5.15 icmp_seq=3 Destination Host Unreachable
From 192.168.5.15 icmp_seq=4 Destination Host Unreachable
From 192.168.5.15 icmp_seq=6 Destination Host Unreachable
From 192.168.5.15 icmp_seq=7 Destination Host Unreachable
From 192.168.5.15 icmp_seq=8 Destination Host Unreachable
From 192.168.5.15 icmp_seq=10 Destination Host Unreachable
From 192.168.5.15 icmp_seq=11 Destination Host Unreachable
From 192.168.5.15 icmp_seq=12 Destination Host Unreachable
^Z
[3]+ Stopped ping -I eth0 169.254.0.0
[root@dhcppc0 Desktop]# traceroute 8.8.8.8
traceroute to 8.8.8.8 (8.8.8.8), 30 hops max, 60 byte packets
1 * * *
2 * * *
3 * * *
4 * * *

[root@localhost ~]# service network restart

Code:

Shutting down interface eth0:                              [  OK  ]
Shutting down loopback interface:                          [  OK  ]
Bringing up loopback interface:                            [  OK  ]
Bringing up interface eth0:  Determining if ip address 192.168.5.15 is already in use for device eth0...

[ OK ]

[root@localhost ~]#vi /etc/resolv.conf

Code:


# Generated by NetworkManager


# No nameservers found; try putting DNS servers into your
# ifcfg files in /etc/sysconfig/network-scripts like so:
#
# DNS1=xxx.xxx.xxx.xxx
# DNS2=xxx.xxx.xxx.xxx
# DOMAIN=lab.foo.com bar.foo.com

#vi /etc/sysconfig/network-scripts/ifcfg-eth0

Code:

DEVICE=eth0
TYPE=Ethernet
BOOTPROTO=none
NM_CONTROLLED=no
ONBOOT=yes
IPADDR=192.168.5.15
NETMASK=255.255.255.0
GATEWAY=192.168.5.2
HWADDR=4c:72:b9:21:ba:e4
IPV6INIT=no
USERCTL=no

[root@localhost ~]# vi /etc/sysconfig/network

Code:

NETWORKING=yes
HOSTNAME=localhost

my network manager configuration is

Code:

[root@localhost ~]# service NetworkManager start
Setting network parameters...                              [  OK  ]
Starting NetworkManager daemon: 

[root@localhost ~]# service NetworkManager status
NetworkManager (pid  1835) is running...

[root@localhost ~]# chkconfig network on
[root@localhost ~]# chkconfig --list | grep Network
NetworkManager 	0:off	1:off	2:on	3:on	4:on	5:on	6:off

[root@localhost ~]#

please someone help me .....
I cannot analyze what is the problem..
please.

lazydog · 04-24-2015, 09:16 AM

You have configuring an ip address on eth0. Is eth0 plugged directly into the ISP device? If so then eth0 should be DHCP not STATIC.
Should look something like this:

Code:

DEVICE=eth0
TYPE=Ethernet
BOOTPROTO=DHCP
NM_CONTROLLED=no
ONBOOT=yes
HWADDR=4c:72:b9:21:ba:e4
IPV6INIT=no
USERCTL=no

pandy669@gmail.com · 04-27-2015, 03:17 AM

thanks for your reply
I am not connecting my system directly with ISP.
sorry I have formatted my system.After formated my system internet is working fine.I have been accessing the the internet from the switches.we are 30 users using the internet from that switch.
Now i am accessing the internet by DHCP.we have two ISP.
one by firewall and another one without firewall.
I am accessing the internet without firewall intermediate.
Before that while I had been accessing the internet often internet connection will disconnected.
I was thinking this is happening by network.
Before a week only the both internet was not connecting .
then only I have found that problem ,that is by my system.
If I unplug the ehternet card from computer and restarted the ISP ,the ineternet was working fine.
Noe i have formated my system .
And also i am fearing to give a static ip in my system.
when those probelm had been occured I was using static ip.
So now my problem is can i use static (i need to use static ip).
If i use static ip ,is the network will down again?
And why that problem was happening ?
sorry If i entered incurrected meaning.
thanks in advance.

lazydog · 04-27-2015, 08:16 AM

Can you post the output of ifconfig now that you are on DHCP? We might be able to find the issue and help you get the correct setup for using static IP.

pandy669@gmail.com · 04-27-2015, 08:27 AM

yeah sure.
this is my output of ifconfig

Code:

[root@dhcppc0 svn]# ifconfig
eth0      Link encap:Ethernet  HWaddr 4C:72:B9:21:BA:E4  
          inet addr:192.168.5.3  Bcast:192.168.5.255  Mask:255.255.255.0
          inet6 addr: fe80::4e72:b9ff:fe21:bae4/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:305633 errors:0 dropped:0 overruns:0 frame:0
          TX packets:226148 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:293325631 (279.7 MiB)  TX bytes:38310649 (36.5 MiB)
          Interrupt:20 Memory:fe500000-fe520000 

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:1085 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1085 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:246802 (241.0 KiB)  TX bytes:246802 (241.0 KiB)

And this is my /etc/sysconfig/network-scripts/ifcfg-eth0 file :

Code:

DEVICE=eth0
TYPE=Ethernet
UUID=b943d502-2825-43e1-b9a4-87da35f5b6b2
ONBOOT=no
NM_CONTROLLED=yes
BOOTPROTO=dhcp
HWADDR=4C:72:B9:21:BA:E4
DEFROUTE=yes
PEERDNS=yes
PEERROUTES=yes
IPV4_FAILURE_FATAL=yes
IPV6INIT=no
NAME="System eth0"

lazydog · 04-27-2015, 08:46 AM

And can you post the output from

Code:

 route -n

pandy669@gmail.com · 04-27-2015, 09:13 AM

thanks and this is my route -n output:

Code:

Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
192.168.5.0     0.0.0.0         255.255.255.0   U     1      0        0 eth0
0.0.0.0         192.168.5.2     0.0.0.0         UG    0      0        0 eth0

And Now I am accesing the internet without firewall.
To forward my local ip to public ip I need to be connect with the firewall .
can i connect through firewall to access the internet.

pandy669@gmail.com · 04-27-2015, 09:46 AM

Also when I have been restarting the appache

I am getting the following

Code:

[root@dhcppc0 svn]# service httpd restart 
Stopping httpd:                                            [  OK  ]
Starting httpd: httpd: apr_sockaddr_info_get() failed for dhcppc0
httpd: Could not reliably determine the server's fully qualified domain name, using 127.0.0.1 for ServerName

lazydog · 04-27-2015, 01:55 PM

What is the range of the DHCP scope?

httpd is failing because it is looking for your FQDN.

pandy669@gmail.com · 04-28-2015, 03:06 AM

DHCP limit is from 192.168.5.3 to 255
we are using two ISP.
but we have only one switch.
So the two networks are assigned to 192.168.5.x series
one network is using by providing static ip.Another one DHCP.

lazydog · 04-28-2015, 08:13 AM

So are you managing your network interfaces with NetworkManager?

pandy669@gmail.com · 04-28-2015, 09:27 AM

sorry I dont know about network manager
I have configured the dhcp by editing the network connections graphically.
Before problem have been occured I had been configuring the network by editing the /etc/sysconfig/network-scripts/ifcfg-eth0 file only.
Now why I am not editing by this eth0 file means ,
because thinking about there may be a problem occured again.

lazydog · 04-28-2015, 11:50 AM

So when you set the interface to DHCP everything works. But when you try to make it static it doesn't work. Are you sure yopu are not using an ip address that is already assigned? This is what it is beginning to sound like.

You say you don't know about NetworkManager but this line stated that it is controlling the interface;

Code:

NM_CONTROLLED=yes

pandy669@gmail.com · 04-29-2015, 01:54 AM

when I choose DHCP ,Networkmanager option was automaticaly enabled.I didn't enter in that eth0 file.
And If i use static ip (doesn't assign to any system),will there any problem on network or in my system ?
network manager what will do.
Am i need to disable the NetworkManager ?
My hostname also automatically changed to dhcppc0.

lazydog · 04-29-2015, 07:41 AM

I do not believe this will cause you any problems allowing NM to control your network interfaces. You will just need to start NM and set a static ip for your interface so it is aware that the interface is static.