how to start/bring up a nic at boot that has no IP

Discussion in 'Server Operation' started by systimax, May 11, 2007.

  1. systimax

    systimax New Member

    With Linux you can have nics that have no ips active. Can someone tell me how to get a nic to start at boot that has no IP?

    If i do a ifconfig -a it shows all 3 physical adapters however the only one that activates at boot is the one that has a ip address assigned to it.

    After it boot the server I can manually do a ifconfig ethx up and it does what i need it to do.

    I just need to learn how to add that nic to be brought up automatically when the other nic with the ip address does. I'm running Ubuntu server but im sure this applies to many nix distros.



    If you want to know why I am asking to activate a nic with no ip here is what you can do with a nic with no ip

    "For example a Ubuntu installed with Vmware server or workstation.

    You can bridge nics to virtual switches when the nic does not have a ip. Then only the virtual machines have ip addresses. That way if you have a server with 2 physical nics one nic can be bridged to a dmz with no ip adress and one can be bridged to the internal lan with an ip.

    With no firewall any vm in the DMZ can not enter the internal lan. Simply because the bridged nic only has vmware protocol and no tcp address or bindings

    This is recommended for security.

    And it works when i manually do it. Ifconfig eth1 up bam my ipless nic starts to flow with vm traffic. and the vm hosts can web browsing ..what ever

    Another example is using Snort you add nics with no ips for inline scanning Another is Ethereal, You can also bridge nics in Ipfw with no ips to create a sort of invisible firewall"
  2. smali

    smali New Member


    In /etc/sysconfig/networking-scripts/ifcfg-ethX add ONBOOT=YES
  3. systimax

    systimax New Member

    thanks but this wont work for Ubuntu Onboot is not supported

    there is no networking-scripts folder or file

    and the network config is in /etc/network/ in a file called interfaces

    So i guess this is a debian ubuntu thing
  4. falko

    falko Super Moderator ISPConfig Developer

    I think something like

    auto ethx
    iface ethx inet static
    in /etc/network/interfaces should work.

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