dhcpd configuration for dynamic IP DNS? - Help

This is a discussion on dhcpd configuration for dynamic IP DNS? - Help ; I currently have a Linux system that is firewalling my home network and providing dhcp service. My ISP (comcast) has decided that they are not longer able to provide static DNS IP's. So now I need to figure out how ...

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Thread: dhcpd configuration for dynamic IP DNS?

  1. dhcpd configuration for dynamic IP DNS?

    I currently have a Linux system that is firewalling my home network and
    providing dhcp service. My ISP (comcast) has decided that they are not
    longer able to provide static DNS IP's. So now I need to figure out how to
    make dhcpd pick up the new DNS IP from the interface attached to the outside
    world and report it back to all the computers on my network. Does anyone
    know how to do this?

    I'm also thinking that maybe I can do this in the routing table using a
    static local IP for DNS that is then routed to the IP provided by my ISP.
    Any thoughts on how this might be done?

    Thanks!




  2. Re: dhcpd configuration for dynamic IP DNS?

    Hi Joe,

    Thanks for the reply. You've mistaken my problem, probably my fault for not
    explaining it clearly. I know what a DNS is. I haven't had a static IP in
    years, what I was talking about was the IP address for Comcast's DNS
    servers. By static I meant that they (the DNS servers) were always to be
    found at the same IP address. That was probably bad nomenclature on my part.
    As far as I know, my LAN machines do need to know the external IP address of
    the DNS servers if I want to access the internet. You need a DNS server to
    resolve a domain name. If you don't have the IP address for the DNS server,
    you're hosed. Am I missing something obvious here?

    I have always used dhcp. My linux machine is used as a firewall. This means
    it has one NIC connected to the outside world (Comcast) and another
    connected to my home LAN. The NIC connected to the outside world, call it
    eth0, is configured using dhcp from Comcast's dhcp server. This server
    provides the IP address for eth0 as well as DNS server IP's. This is all
    fine and good. I have no problems here.

    The other NIC, call it eth1, is connected to my LAN. My linux machine is the
    dhcp server for my home LAN. So all my local computers get their IP, and DNS
    information from my linux dhcp server on eth1. The problem I have is how to
    configure my dhcp server to report the proper Comcast DNS IP's to my local
    machines. In the past, Comcast has used the same IP's for their DNS servers.
    These DNS IP's can be acquired from Comcast's dhcp server, but up to now
    they have never changed. So I just configured the dhcpd daemon on eth1 to
    report the fixed/static/constant IP's for the Comcast DNS servers. Now
    Comcast wants to be able to change these servers IP's around at will. This
    is not a concern for eth0 because it will pick up the current DNS IP from
    Comcast's dhcp server, but I need to figure a way to get the DNS information
    acquired on eth0 from Comcast's dhcp server into my local dhcp server on
    eth1 so it can then configure my LAN machines correctly. I hope that is
    clear.

    I think this is a distribution independent problem but for the record it
    RedHat v8.x (yes it's updated as much as possible and does not have public
    servers). This is probably stupidly easy but I don't know how to do it...

    Thanks!



    "Joe Zeff" wrote in message
    news:ltka32h7phu4jfonvphsj3jiq1admt1t4q@4ax.com...
    > On Thu, 6 Apr 2006 00:47:43 -0700, wrote:
    >
    >>I'm also thinking that maybe I can do this in the routing table using a
    >>static local IP for DNS that is then routed to the IP provided by my ISP.
    >>Any thoughts on how this might be done?

    >
    > You do know, don't you, that "DNS IP" is incorrect?[1] You had a
    > static IP, now you're on DHCP. I'd suggest that you go into your
    > network configuratin and set it to DHCP. How you do that and where
    > depends on your distro, which you didn't mention. Once that's done,
    > and you've picked up your current IP, everything should work fine;
    > your internal machines have no more need to know external IP now than
    > they did before.
    >
    > [1]DNS is used for translating domain names to IP addresses. Unless
    > you are hosting a domain at home, DNS doesn't come into play.
    >
    > --
    > Joe Zeff
    > The Guy With the Sideburns
    > Spammers. Can't live with them, can't flay them
    > and throw them into a bath of coarse sea salt.
    >
    http://www.lasfs.org http://home.earthlink.net/~sidebrnz





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