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New Install of CentOS 6, Networking Is Not Working

Posted: 2011/08/01 21:54:41
by jmneedham
Greetings All:

I have read the other posts about this problem and actually did use the "configure network" at the name this computer screen during install. I have checked the network scripts folder and edited the ifcfg-eth0 and changed my DNS settings to the IP addresses for openDNS. I was unable to ping any external site by name from the start, I had setup my initial configuration with the IP for my gateway initially.

At this point if you ping microsoft.com, for example, the box seems to be trying to do it and then comes back with a message unknown host: microsoft.com error.

Again it has done this since I first brought the box online, only the error was immediate with my initial config.

I am actually running the CentOS box headless and I am logged on via SSH to do everything. (Obviously, when I installed, I had a keyboard, mouse and monitor hooked to the box).

My ISP is Comcast and it is their router/modem -- it uses 10.0.0.x addresses and I have assigned 10.0.0.100 to my CentOS machine and the modem is the 10.0.0.1 which is the gateway address.

Not sure what is happening here, but all the examples of the ifcfg-eth0 script seem to match fine with what my config is.

Hope someone can offer some help.

Re: New Install of CentOS 6, Networking Is Not Working

Posted: 2011/08/01 22:04:23
by TrevorH
I think we'll need to see the output from the getinfo.sh script that you can find in the FAQ and Readme First forum to be able to help. I would ask if you can ping the opendns servers by IP address first.

Re: New Install of CentOS 6, Networking Is Not Working

Posted: 2011/08/01 23:02:22
by jmneedham
Hey and thanks for the response so far. I have pasted the file for my getinfo.sh [url=http://pastebin.centos.org/37691]Mike Needham getinfo[/url].

I can not ping the IP from my machine either.

I have also uploaded my ifcfg-eth0 file [url=http://pastebin.centos.org/37692]Mike's ifcfg-eth0 file[/url]

Both are in pastebin for a day.

I am still not able to get out but I am able to ssh into the box still and so on.

Re: New Install of CentOS 6, Networking Is Not Working

Posted: 2011/08/01 23:22:26
by TrevorH
Can you post the output from the following commands, run by root, since it didn't appear to be in the pastebin stuff.

[code]
/sbin/ifconfig
ip route
iptables-save
cat /etc/resolv.conf
[/code]

Re: New Install of CentOS 6, Networking Is Not Working

Posted: 2011/08/01 23:30:57
by jmneedham
As requested, the output of all the requested files: [url=http://pastebin.centos.org/37693]More Mike System Info[/url]

Re: New Install of CentOS 6, Networking Is Not Working

Posted: 2011/08/01 23:37:43
by TrevorH
Whatever it is that's wrong is not immediately obvious from that lot. Hope someone else is not as blind as me :-)

Re: New Install of CentOS 6, Networking Is Not Working

Posted: 2011/08/02 10:55:58
by r_hartman
Looks good to me. But you apparently have a DNS issue. So could you answer [b]Trevor[/b]'s earlier question:
Can you ping the DNS servers defined in your resolv.conf?
If not, can you ping your gateway?
This might just be a modem problem, nothing to do with your CentOS box.

Re: New Install of CentOS 6, Networking Is Not Working

Posted: 2011/08/02 11:33:15
by jmneedham
As I did state in one of my replies, yes I can ping the gateway and in fact, I am able to login into the box via SSH on the LAN side of my modem. No I can not ping the DNS servers by IP.

The other boxes get out just fine that are connecting to the same modem.

Re: New Install of CentOS 6, Networking Is Not Working

Posted: 2011/08/02 12:14:19
by jmneedham
This problem is solved. It turns out that the cable modem/router had to know about the static IP before it will let the box go outside of the local LAN. Once I put the box into the rotuer as static (with MAC address), everything is working properly now.

Thanks for the all the help. BTW: If anyone else has Comcast and they have the new wireless gateway from SMC, this will need to be done to allow your box onto the Internet. (Unless you are using DHCP of course).

New Install of CentOS 6, Networking Is Not Working

Posted: 2011/08/02 17:11:24
by pschaff
In my experience making DHCP behave the way you want it to generally makes life easier than working around it with a fixed IP address. You may want to read [url=http://wiki.centos.org/TipsAndTricks/EmulateFixedAddressByDHCP]Emulate a fixed IP address using MAC address with DHCP[/url].