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Windows Server 2008 R2 Thread, DHCP not updating Hostname in Technical; I seem to have a whole bunch of DHCP entries that do not have a corresponding host name (see attached) ...
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    RabbieBurns's Avatar
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    DHCP not updating Hostname

    I seem to have a whole bunch of DHCP entries that do not have a corresponding host name (see attached)

    dhcpq.PNG

    This is causing problems with nslookup and things that rely on it..

    Not entirely shure what is causing this.

    Any ideas?

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    ZeroHour's Avatar
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    Do you have any settings set to limit record updates?

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    RabbieBurns's Avatar
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    not that im aware of, no. Out of about 2000 devices theres only about 30-40 that dont have a hostname.

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    Quote Originally Posted by RabbieBurns View Post
    not that im aware of, no. Out of about 2000 devices theres only about 30-40 that dont have a hostname.
    I take it you have set the DHCP server to update DNS records? If so, have you done so for all DHCP leases, or just for leases when the clients request so?

    It might also be worth checking the current IP address of the devices in question (either from the clients themselves or the DHCP server), and see if there are any clashes in DNS with this address - particularly in reverse lookup. If so, check the permissions of these entries against other entries and see if there are any discrepancies.

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    RabbieBurns's Avatar
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    These are my settings can you please tell me if there is something not quite right:

    dhcp1.PNGdhcp2.PNGdnszone.PNG

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    Quote Originally Posted by RabbieBurns View Post
    These are my settings can you please tell me if there is something not quite right:
    Thoes settings look OK to me. Certainly the DNS settings are set the same as on our DHCP server, although I know some people say that having the DHCP server manage DNS entries might not be the best thing. The scavange settings also look OK, although off the top of my head I cannot remember best practice for ratios of DHCP leases, refresh and non-refresh times. There is a pretty good guide here that covers the lot - DHCP, Dynamic DNS Updates , Scavenging, static entries & time stamps, the DnsUpdateProxy Group, and DHCP Name Protection - AD and Exchange Quantum Singularity

    One more quick question - I take it the mac addresses for the network adaptors on the host PCs match the uniquie ID entries on the DHCP leases?

    One thing you could try - deleting forward and reverse entries for a single device in that address scope with a missing name entry in DHCP (ideally a test PC or similar) then restarting it. See if creating a new entry in DNS (as opposed to refreshing an exsiting entry) solves the problem. It probably won't, but it's an easy thing to try that shouldn't break anything else.

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    RabbieBurns's Avatar
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    none of the entries in DHCP that are missing a hostname have an entry in DNS.

    This is the problem.

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    Quote Originally Posted by RabbieBurns View Post
    none of the entries in DHCP that are missing a hostname have an entry in DNS.

    This is the problem.
    What devices are they that have the missing DNS entries? Printers/Windows Machines/Tablets etc?

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    RabbieBurns's Avatar
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    The ones Im caring about that are causing issues are windows 7 domain joined devices. There may be tablets and phones in there (printers are all static assigned) but there is an issue where our Firewall/filter uses DNS lookups to match the current machine name (which it gets from monitoring logon events in DC) to an IP.

    For these devices where theres no reverse dns lookup available, auto-authentication to the firewall fails, and the users drop to NTLM authentication and have to enter their credentials in a pop up box which is a PITA.

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    ajs
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    I've seen this with devices that have a hostname longer than 15 characters, DHCP will just display a blank rather than trying to truncate the name.

    Could be worth a look.

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