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Old 08-22-2011, 12:52 PM   #1
nuancechuck
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Cent 6.0 Losing IP assigned by dhcp everytime I reboot


Hi,
I just built a Cent 6.0 box, it is set for DHCP. Everytime I reboot It doesn't receive an address. To fix I just have to go into network settings and hit apply. I have worked with Windows OS for years but am new to Linux. Does anyone know why this would happen and the solution to this?
Thanks!
Chuck
 
Old 08-22-2011, 03:12 PM   #2
T3RM1NVT0R
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Hi there,

Welcome to LQ!!!

We need to check whether NIC is configured to get IP at the time of Boot. Please paste the output of the following command:

Code:
cat /etc/sysconfig/network-scripts/ifcfg-eth0

Last edited by T3RM1NVT0R; 08-22-2011 at 03:23 PM.
 
Old 08-23-2011, 10:05 AM   #3
nuancechuck
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Output from cat /etc/sysconfig/network-scripts/ifcfg-Auto_eth0

Hi and thanks,
Thare was no file called ifcfg-eth0 but there was one called ifcfg-Auto_eth0. Here is the output from that file:
TYPE=Ethernet
BOOTPROTO=dhcp
DEFROUTE=yes
IPV4_FAILURE_FATAL=yes
IPV6INIT=no
IPV6_AUTOCONF=yes
IPV6_DEFROUTE=yes
IPV6_PEERDNS=yes
IPV6_PEERROUTES=yes
IPV6_FAILURE_FATAL=yes
NAME="Auto eth0"
UUID=3de80abd-c464-49ad-94d6-68344619dd33
ONBOOT=yes
DEVICE=Auto_eth0
USERCTL=no
HWADDR=00:1A:A0:BE:66:9B
PEERDNS=yes
PEERROUTES=yes
 
Old 08-23-2011, 04:16 PM   #4
T3RM1NVT0R
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Alright, from the output you pasted it is configured to start at boot as it says ONBOOT=yes. However, I am not quite convinced that there is no file with the name ifcfg-eth0. If this file is not there then there should be a file eth1 or something similar. What is the output if you type:

Code:
ifconfig
If the output of the above command shows Auto_eth0 then we will look forward for editing the file.

We also have to make sure that the NetworkManager service is configured to start at boot. This service is responsible for loading dhclient which in turn gets you an IP address from dhcp service.

You can check this service status using:

Code:
chkconfig NetworkManager status
If it shows that the service is configured to start on all run levels (i.e. 2,3,4,5) then it is ok else you can enable it by running the following command:

Code:
chkconfig NetworkManager on
 
Old 08-23-2011, 11:23 PM   #5
jraz
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Does it have to be DHCP? Can it have a static address? If no static is available, can you set a reservation on the MAC address in the DHCP server? Also there is a check box in the lower left making the config available to all users. Just a shot in the dark on the last bit.

I set reservations in my router at home. Nothing gets connected for my network without one. Of course it is small and easy to manage. At work I use reservations for printers and other devices. I could use static IP's but often they get moved or replaced. Re-entering a MAC is much easier to set and manage.
 
Old 08-24-2011, 05:18 PM   #6
nuancechuck
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strange

Hi, Sorry to be a pain.
I am able to run chkconfig NetworkManager on and chkconfig NetworkManager off but when I try chkconfig NetworkManager status it justy gives me:

[Usage: chkconfig [--list] [--type <typy>] [name]
chkconfig --add <name>
chkconfig --del <name>
chkconfig --override <name>
chkconfig [--level] <levels> [--type <type>] <on|off|reset|reset priorities>


Also Here is a ls of the /etc/sysconfig/network-scripts directory:
-rw-r--r--. 1 root root 221 Aug 24 03:52 ifcfg-Auto_eth0
-rw-r--r--. 1 root root 254 Sep 1 2010 ifcfg-lo
lrwxrwxrwx. 1 root root 20 Jul 14 05:13 ifdown -> ../../../sbin/ifdown
-rwxr-xr-x. 1 root root 627 Sep 1 2010 ifdown-bnep
-rwxr-xr-x. 1 root root 5059 Sep 1 2010 ifdown-eth
-rwxr-xr-x. 1 root root 781 Sep 1 2010 ifdown-ippp
-rwxr-xr-x. 1 root root 4246 Sep 1 2010 ifdown-ipv6
lrwxrwxrwx. 1 root root 11 Jul 14 05:13 ifdown-isdn -> ifdown-ippp
-rwxr-xr-x. 1 root root 1481 Sep 1 2010 ifdown-post
-rwxr-xr-x. 1 root root 1064 Sep 1 2010 ifdown-ppp
-rwxr-xr-x. 1 root root 651 Sep 1 2010 ifdown-routes
-rwxr-xr-x. 1 root root 1367 Sep 1 2010 ifdown-sit
-rwxr-xr-x. 1 root root 1431 Sep 1 2010 ifdown-tunnel
lrwxrwxrwx. 1 root root 18 Jul 14 05:13 ifup -> ../../../sbin/ifup
-rwxr-xr-x. 1 root root 13454 Sep 1 2010 ifup-aliases
-rwxr-xr-x. 1 root root 859 Sep 1 2010 ifup-bnep
-rwxr-xr-x. 1 root root 9944 Sep 1 2010 ifup-eth
-rwxr-xr-x. 1 root root 11971 Sep 1 2010 ifup-ippp
-rwxr-xr-x. 1 root root 10679 Sep 1 2010 ifup-ipv6
lrwxrwxrwx. 1 root root 9 Jul 14 05:13 ifup-isdn -> ifup-ippp
-rwxr-xr-x. 1 root root 727 Sep 1 2010 ifup-plip
-rwxr-xr-x. 1 root root 954 Sep 1 2010 ifup-plusb
-rwxr-xr-x. 1 root root 2364 Sep 1 2010 ifup-post
-rwxr-xr-x. 1 root root 4154 Sep 1 2010 ifup-ppp
-rwxr-xr-x. 1 root root 1712 Sep 1 2010 ifup-routes
-rwxr-xr-x. 1 root root 3490 Sep 1 2010 ifup-sit
-rwxr-xr-x. 1 root root 2482 Sep 1 2010 ifup-tunnel
-rwxr-xr-x. 1 root root 3770 Sep 1 2010 ifup-wireless
-rwxr-xr-x. 1 root root 4508 Sep 1 2010 init.ipv6-global
-rwxr-xr-x. 1 root root 1125 Sep 1 2010 net.hotplug
-rw-r--r--. 1 root root 9966 Sep 1 2010 network-functions
-rw-r--r--. 1 root root 29835 Sep 1 2010 network-functions-ipv6

I'm liking linux stuff though far more interesting than windows.

I do not have the option of a static as another group here gives them out and I'm just trying to learn this so thats not good enough to get one.

Thanks!
Chuck
 
Old 08-25-2011, 03:10 AM   #7
T3RM1NVT0R
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Hi there,

Sorry it was my mistake it is not chkconfig NetworkManager status. It should be chkconfig --list NetworkManager.

If your NetworkManager is showing as on on all the run levels then take a backup of: /etc/sysconfig/network-scripts/ifcfg-Auto_eth0. When I say backup just copy it somewhere and then make the following changes:

TYPE=Ethernet
HWADDR=00:1A:A0:BE:66:9B
BOOTPROTO=dhcp
ONBOOT=yes
DEVICE=Auto_eth0
USERCTL=no

Save the file and exit. Reboot the system and check if you get IP from DHCP or not.

If NetworkManager is showing as off then do chkconfig NetworkManager on

Last edited by T3RM1NVT0R; 08-25-2011 at 03:12 AM.
 
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