DDNS Update from a Linux box with a static IP
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Thread: DDNS Update from a Linux box with a static IP

  1. #1
    King Tutorial-ankhamun
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    DDNS Update from a Linux box with a static IP

    I was playing around to see if I could DOS on of my own boxed by having another device come up with the same host name. In the process I killed the Dynamic DNS entry for a box (and I'm not an admin on the DNS server). Anyone know how I can send DDNS Update from a Linux box with a static IP? Thanks.

  2. #2
    Senior Member
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    There's usually a way with most DDNS providers to log in to your account and force a manual update, giving it the IP. I know when I do a manual update with DynDNS, it fills out a IP address form for me, but I am free to change the form if so inclined.

    Or try forcing an update manually from the DDNS client, using whatever software handles the updates normally.

    Can't really help out much more w/o some more info...

    [edit]
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  3. #3
    Senior Member Maestr0's Avatar
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    Are you talking about a DDNS provider like DynDNS, or simply a DDNS server, aka you brought up the client with the same hostname on DHCP and the DNS server allowed it to overwrite the original entry?

    -Maestr0
    \"If computers are to become smart enough to design their own successors, initiating a process that will lead to God-like omniscience after a number of ever swifter passages from one generation of computers to the next, someone is going to have to write the software that gets the process going, and humans have given absolutely no evidence of being able to write such software.\" -Jaron Lanier

  4. #4
    King Tutorial-ankhamun
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    Thanks, but what I mean is DDNS as in the Microsoft DNS server we run at work. I think I may have figured out you do do it with the nsupdate command. Thanks.

    Glad you like the joke.

  5. #5
    King Tutorial-ankhamun
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    Originally posted here by Maestr0
    Are you talking about a DDNS provider like DynDNS, or simply a DDNS server, aka you brought up the client with the same hostname on DHCP and the DNS server allowed it to overwrite the original entry?

    -Maestr0
    Simply a DDNS server, yep, I brought up a DHCP host with the same name and that killed it. (But I seem to have it fixed now)

  6. #6
    Senior Member Maestr0's Avatar
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    The way most DDNS servers are configured they only allow the updates to the zone to be performed by the DHCP server. So if you wanted to say "trick" it, I would go to the original host, and edit the dhclient.conf and add a option ip-adress IP.ADD.I.WANT line, and then run dhclient to see if you could pull that IP from the pool and let the DHCP server write the update, then go back to static.

    -Maestr0

    edit: If the DNS server allows the clients to update it, then nsupdate should do the trick.
    \"If computers are to become smart enough to design their own successors, initiating a process that will lead to God-like omniscience after a number of ever swifter passages from one generation of computers to the next, someone is going to have to write the software that gets the process going, and humans have given absolutely no evidence of being able to write such software.\" -Jaron Lanier

  7. #7
    King Tutorial-ankhamun
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    nsupdate already did the trick, but thanks for looking into it. I wonder how easy it would be to use the same trick to redirect the mail web server? I just used nsupdate to redirect the DNS name from one of my servers to another, so it would work in theory. I need to look more into how DNS works, we may not be configured securely at work.

  8. #8
    Senior Member Maestr0's Avatar
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    As I said, if configured right the DNS should'nt accept updates from anyone, but of course it can . Typically there is a zone(s) which are only DHCP, and only these zones can be updated, and only by the DHCP server.

    -Maestr0
    \"If computers are to become smart enough to design their own successors, initiating a process that will lead to God-like omniscience after a number of ever swifter passages from one generation of computers to the next, someone is going to have to write the software that gets the process going, and humans have given absolutely no evidence of being able to write such software.\" -Jaron Lanier

  9. #9
    King Tutorial-ankhamun
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    So something like *.workstations.example.com can be updated with ddns and *.servers.example.com can not. Looks like that's not how it's configured, everything is updatable. Guess I'll talk to the guys in net ops.

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