Thread: CentOS 7 Networking issues

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  1. #1 CentOS 7 Networking issues 
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    Hey. I've been trying to install CentOS for the past couple days now. Every time i do, during the install it connects to the network just fine. but then when it boots up after installing, i have issues. I'll try and describe it.

    At first, i could NOT get it to connect. it just would not. nothing at all. so i grabbed a spare NIC and it connected right up, right away. for a few moments. that's to say, it established a connection to my router & was given an address. At that point i tried SSHing in from my desktop, WHICH WORKED.. until i typed root (enter) at that point it lost it's IP and disconnected from the network. i fiddled and fiddled and fiddled around and re-installed a couple times. At the moment, i have it installed with a GUI so i can debug a little easier.

    Here's the really weird thing though. right now, DHCP will give me an address (after some hesitation). I have it set up as a static IP (192.168.1.114) the router sees it, PCs on my network can ping it, it can ping them. safe to say local networking should be up and running right? well, i can't SSH from my desktop on the same network, so that must not be right. The internet also doesn't work, i can't yum update, i can't use a web browser.. but i can ping hosts by name, (like rune-server.org) so... I can ping the internet.. but i can't connect to it. I can ping my server from my network, but i can't ssh to it..

    I'm out of ideas. Should i just use Centos 6?

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  2. #2  
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  3. #3  
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    What's the output of:

    ip a
    ip route
    iptables -L

    Is there anything interesting in dmesg?
    .
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  5. #4  
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    Quote Originally Posted by Graham View Post
    What's the output of:

    ip a
    ip route
    iptables -L

    Is there anything interesting in dmesg?
    Thank you for the reply. booting up to test this now. will edit when i have results

    Edit:
    sorry for photos:

    http://imgur.com/a/QXaiD


    Thinking of trying Fedora instead. Never used it, but my father has & he says it's similarly sourced.

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  6. #5  
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    Is this for a desktop system? If so you'd be much better off running Fedora, which is also from Red Hat.


    On topic of the issue, could you run:

    Code:
    nmcli d show enp4s7
    and

    Code:
    nmcli c show <connection-name>
    where connection name is the value for GENERAL.CONNECTION in the output of `nmcli d show`
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  8. #6  
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    Quote Originally Posted by saifix View Post
    Is this for a desktop system? If so you'd be much better off running Fedora, which is also from Red Hat.


    On topic of the issue, could you run:

    Code:
    nmcli d show enp4s7
    and

    Code:
    nmcli c show <connection-name>
    where connection name is the value for GENERAL.CONNECTION in the output of `nmcli d show`
    No i'm not going to be using this as a desktop computer, i'm going to use it as a dedicated server. I've done it before, and with CentOS 7.

    back OT:

    Code:
    nmcli d show enp4s7
    outputs:
    http://imgur.com/4hmN4dm.png

    and i did

    Code:
    nmcli c show "Auto Ethernet"
    and just got "not found"

    http://i.imgur.com/IYVmVuI.jpg

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    Interestingly you have two routes for your local network (192.168.1.0/24), one of which tries to make all the local network traffic go via the router (which could lead to some sort of interesting loop maybe (?), as the router itself should be directly reachable).

    Try:

    Code:
    ip route del 192.168.1.0/24 via 192.168.1.1 dev enp4s7
    Might also be worth disabling the firewalld stuff, just to be sure that's not interfering? Not sure how that's done as I only use CentOS at work.
    .
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  11. #8  
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    Quote Originally Posted by Graham View Post
    Interestingly you have two routes for your local network (192.168.1.0/24), one of which tries to make all the local network traffic go via the router (which could lead to some sort of interesting loop maybe (?), as the router itself should be directly reachable).

    Try:

    Code:
    ip route del 192.168.1.0/24 via 192.168.1.1 dev enp4s7
    Might also be worth disabling the firewalld stuff, just to be sure that's not interfering? Not sure how that's done as I only use CentOS at work.
    sigh.. okay did that, but i also seem to have another issue that wasn't happening last time i had the thing on.. i can't get the networking service to restart.. http://imgur.com/wstArZK.png

    Edit:
    Ok, got network to restart by using nmtui to set it back to full DHCP and deleting the 2 other network interfaces associated with the onboard NIC, Prior to this, i could ping out to the internet, Now i can not. I am connected to my network, and i can ping hosts on my network, but i once again, can not ping out. This is very confusing to me. I'm about to try setting it back to static to see if that'll let me ping out. I suppose it could be the static DNS i had set causing me not to be able to ping out... i guess.


    Edit2: k back to static, still connected to my network, still can ping hosts on my network, still can't ping out.

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  12. #9  
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    Disabling firewalld can be done with `systemctl stop firewalld && systemctl disable firewalld`, however, you can get the logs for a systemd unit using journalctl:

    Code:
    journalctl -u networking
    should tell you exactly why networking failed to start.

    Now that you've deleted some of your connections what do you have now for:

    Code:
    nmcli c show
    and try bringing the interface up manually using ifup, see: networking - Solving “RTNETLINK answers: File exists” when running ifup - Raspberry Pi Stack Exchange
    "Im so bluezd out of my box.
    Im so fkd i canr even sens makeas Smoke blunt 420hash e tizday" - A legendary guy (1993 - 2015)
    Quote Originally Posted by nmopal View Post
    I will be creating a grimy dubstep song using these lyrics and vocaloid please prepare your bodies
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  13. #10  
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    Quote Originally Posted by Jaiden Watling View Post
    Edit2: k back to static, still connected to my network, still can ping hosts on my network, still can't ping out.
    What's the "ip route" output now? This could imply you're missing a default route.
    .
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