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  1. #1
    Join Date
    Jun 2012
    Posts
    102

    Angry KVM & Network Card Bridging, having problems.

    I've read a ton of tutorials and documents on setting up KVM and I always fall over when I get to the part with bridging the network.

    I have a dedicated server with several public IP addresses assigned to me. I'd like to set up bridging so the guest operating systems can be assigned public static ip addresses. Should be simple/common right? Problem is every time I bridge the eth0 or my backup eth0:0 with a bridge interface, I completely lose network connectivity.

    Every tutorial I follow leads to the same conclusion. No connectivity!

    One confusion point I keep running into is all the KVM/Bridging tutorials say to set up the bridge interface as DHCP. Setting the bridge up as DHCP or Static does not make a different to the loss of connection, but I'm still not sure how to do that part either. Why would I set up DHCP if I need to give my guests static and public IPs?

    So can anyone expand on what I need to do? What am I doing wrong?

    Working on CentOS 6.2 here.


    Thanks.

  2. #2
    Join Date
    May 2009
    Location
    Markham, Canada
    Posts
    458
    Post the contents of your /etc/sysconfig/network-scripts/ifcfg-eth0 file (unmodified) and I will make two "correct" files for you (ifcfg-eth0 and ifcfg-br0).
    Dan
    Check out our premium self-managed SSD VPS

  3. #3
    Join Date
    Jun 2012
    Posts
    102
    THANK YOU! I can't wait to see what I've been doing wrong. This is frustrating.

    Code:
    DEVICE="eth0"
    NM_CONTROLLED="yes"
    ONBOOT=yes
    TYPE=Ethernet
    BOOTPROTO=none
    DEFROUTE=yes
    IPV4_FAILURE_FATAL=yes
    IPV6INIT=no
    NAME="System eth0"
    IPADDR=199.X.X.4
    PREFIX=30
    GATEWAY=199.X.X.1
    DNS1=199.X.X.2
    DNS2=199.X.X.3

  4. #4
    Join Date
    May 2009
    Location
    Markham, Canada
    Posts
    458
    Step 1.
    Back up files:
    /etc/sysconfig/network-scripts/route-eth0
    /etc/sysconfig/network-scripts/ifcfg-eth0

    Step 2.
    Rename /etc/sysconfig/network-scripts/route-eth0 to route-br0:
    Code:
    mv /etc/sysconfig/network-scripts/route-eth0 /etc/sysconfig/network-scripts/route-br0
    Step 3.
    Create /etc/sysconfig/network-scripts/ifcfg-br0 with the following:

    Code:
    DEVICE=br0
    TYPE=Bridge
    ONBOOT=yes
    BOOTPROTO=none
    DEFROUTE=yes
    IPV4_FAILURE_FATAL=yes
    IPV6INIT=no
    NAME="System eth0"
    IPADDR=199.X.X.4
    PREFIX=30
    GATEWAY=199.X.X.1
    DNS1=199.X.X.2
    DNS2=199.X.X.3
    Step 4.
    Create /etc/sysconfig/network-scripts/ifcfg-eth0 with the following:

    Code:
    BRIDGE=br0
    DEVICE="eth0"
    ONBOOT="yes"
    TYPE="Ethernet"
    Step 5.
    service network restart

    What I did is I passed your ifcfg-eth0 file through our "convert to br0" script that we use to set up KVM on our CentOS 6 nodes.
    Dan
    Check out our premium self-managed SSD VPS

  5. #5
    Join Date
    Jun 2012
    Posts
    102
    Don't have a route-eth0. Even did a find. This is the "ls" of my network-scripts directory.

    ifcfg-eth0
    ifcfg-eth0:0
    ifcfg-eth0:1
    ifcfg-lo
    ifdown -> ../../../sbin/ifdown
    ifdown-bnep
    ifdown-eth
    ifdown-ippp
    ifdown-ipv6
    ifdown-isdn -> ifdown-ippp
    ifdown-post
    ifdown-ppp
    ifdown-routes
    ifdown-sit
    ifdown-tunnel
    ifup -> ../../../sbin/ifup
    ifup-aliases
    ifup-bnep
    ifup-eth
    ifup-ippp
    ifup-ipv6
    ifup-isdn -> ifup-ippp
    ifup-plip
    ifup-plusb
    ifup-post
    ifup-ppp
    ifup-routes
    ifup-sit
    ifup-tunnel
    ifup-wireless
    init.ipv6-global
    net.hotplug
    network-functions
    network-functions-ipv6
    Also, this one bridge will let me statically assign public IPs to the guests?
    Last edited by ChaosInMind; 07-02-2012 at 09:27 PM.

  6. #6
    Join Date
    May 2009
    Location
    Markham, Canada
    Posts
    458
    If you do not have any custom routes then you can disregard that step.
    Yes, the bridge will allow you to assign public IPs to guests.
    Dan
    Check out our premium self-managed SSD VPS

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