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ifconfig ?? ? - Linux Setup, Configuration & Administration

hello one and all, is ifconfig the ultimate source to see the real IP address for a particular network interface (NIC)? for instance, in dialup, dsl, or cable modem where the IPs are dynamic, is ifconfig always always the best way to know the current IP address? for instance, if the cable modem changes IP address with the computer rebooting, would ifconfig know of the change in the IP address shortly after the cable modem has changed IP addresses? thanx for entertaining my questions. lucas...

  1. #1

    Default ifconfig ?? ?

    hello one and all,

    is ifconfig the ultimate source to see the real IP address for a particular
    network interface (NIC)? for instance, in dialup, dsl, or cable modem where
    the IPs are dynamic, is ifconfig always always the best way to know the
    current IP address? for instance, if the cable modem changes IP address
    with the computer rebooting, would ifconfig know of the change in the IP
    address shortly after the cable modem has changed IP addresses?

    thanx for entertaining my questions.

    lucas


    lucas Guest

  2. #2

    Default Re: ifconfig ?? ?

    lucas <net> wrote: 

    Unless you have some other machine/service performing NAT on it...
     

    ifconfig read the NIC and the kernel data, so, he is reading the
    data "live".

    Davide
    Davide Guest

  3. #3

    Default Re: ifconfig ?? ?

    On Mon, 27 Oct 2003 14:27:03 GMT, lucas wrote: 

    Hard to say because of the " ultimate source" requirement.
    ifconfig will give the ip address for the current status of the nic.
     

    Yes.
     

    That is kinda a junky question as written. You appear to be thinking ip
    addresses are changing while booting. It is not a random process, it
    is a locksteped process.

    At some point in the booting process, the pc's dhcp client broadcasts
    a request to the dhcp server. At that time, the dhcp server gives out
    the ip address that the OS will assign to the nic.

    The dhcp server also sends the time that the lease on the ip address
    will be valid. Half way through the lease time your dhcp client will ask
    the dhcp server to renew the lease. Your client will receive a lease
    renewal, if not, it will continue to retry to get the lease renewed.

    The dhcp server may not renew the lease on the current ip address
    but assign your system a new ip address.
    Your dhcp client will then run a script to get the new ip address assigned
    to the nic.

    Bit Guest

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