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Windows Server 2008 R2 Thread, 2008r2 DHCP facepalm in Technical; Just found out. Apparently you can't just add dhcp reservations willy nilly any more . The migration installation team at ...
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    browolf's Avatar
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    2008r2 DHCP facepalm

    Just found out. Apparently you can't just add dhcp reservations willy nilly any more . The migration installation team at Easter never mentioned it.

    This is a major problem.

    All our classrooms require static ips in a subnet per room arrangement. The classrooms use 192.168.x.y where x is different for different rooms.

    Everything else gets dhcp. the lease pool is 192.168.105.1 - 192.168.109.254

    Am I right in thinking the lease pool has to cover everything and statics have to be excluded?

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    plexer's Avatar
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    Static IP and DHCP Reservation are not the same thing, they acheive the same result.

    You don't have to include the static ip's in the address ppol but you may as well and then exclude the ones you want to use for statics or reservations.

    Ben

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    if your classrooms are 192.168.100.0, 192.168.101.0, 192.168.102.0, and your dhcp scope is 192.168.105.1 - 192.168.109.254 this is ok because they dont overlap.

    If they do overlap, you will need to create the scope and then an exclusion

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    browolf's Avatar
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    Quote Originally Posted by plexer View Post
    Static IP and DHCP Reservation are not the same thing, they acheive the same result.

    You don't have to include the static ip's in the address ppol but you may as well and then exclude the ones you want to use for statics or reservations.

    Ben
    I'm not sure what you're telling me here. Also I may have explained the situation badly.
    What I'm calling 'statics' are computers that need a specific ip. ~ the reservations (as opposed to ones that can have any old ip).

    It won't let me add a reservation. When I try it says "the specified DHCP client is not a reserved client"
    Last edited by browolf; 15th June 2011 at 02:38 PM.

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    if you want reservation outside yor main dhcp scope cant you create a 2nd(or 3rd 4th ...) scope and shove the reservations in there?

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    plexer's Avatar
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    A static ip is just that one that doesn't change i.e you manually go into your computer nic properties and set an ip address, you could pick one which is allready in the pool to be allocated via dhcp and you will then get an ip conflict message.

    A reservation on the other hand is one that is set to be given out by dhcp to a specific mac address.

    On my 2008 R2 dhcp server I can add a reservation using an ip address which has not been excluded.

    Ben

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    browolf's Avatar
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    Quote Originally Posted by sted View Post
    if you want reservation outside yor main dhcp scope cant you create a 2nd(or 3rd 4th ...) scope and shove the reservations in there?
    The scope is 192.168.0.0 ~ nothing can be outside that.

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    bio
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    true.... i mentioned it long time ago here

    bio..

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    Quote Originally Posted by browolf View Post
    I'm not sure what you're telling me here. Also I may have explained the situation badly.
    What I'm calling 'statics' are computers that need a specific ip. ~ the reservations (as opposed to ones that can have any old ip).

    It won't let me add a reservation. When I try it says "the specified DHCP client is not a reserved client"
    I had this and it was simply because that IP had already been given out, so a quick flush of the required IP addresses (I would suggest setting an exclusion up so that it doesn't get given back out again) and then set up the reserved client should work fine .. the only other thing that can effect it is if you have a space on the of the MAC address or something ..

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    browolf's Avatar
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    Quote Originally Posted by bio View Post
    true.... i mentioned it long time ago here

    bio..
    "It is not possible to create a reservation anymore in a scope that holds an ip address that is not used in that scope. For instance you have a scope from 10.10.10.1 to 10.10.10.100 and you want to create a reservation for a PC that needs IP 10.10.10.101. You get a nice error warning that this is not possible"


    do you mean address pool when you say "scope" ?

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    sparkeh's Avatar
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    Good explanation here: *clicky*

    Perhaps I am missing something here, but why would you want to reserve an address that outside of the distribution pool? Its not going to do anything is it?

  12. Thanks to sparkeh from:

    browolf (15th June 2011)

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    Quote Originally Posted by aptproductions View Post
    I had this and it was simply because that IP had already been given out, so a quick flush of the required IP addresses (I would suggest setting an exclusion up so that it doesn't get given back out again) and then set up the reserved client should work fine .. the only other thing that can effect it is if you have a space on the of the MAC address or something ..
    Jeez, the computer labelled as #2 that i've just replaced isn't actually #2...
    The ip i'm trying to reserve is already in use but isn't an existing reservation... (checked...it's a static on that machine)

    DHCP should still allow me to create a reservation then...?

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    Scope = the range of IPs that your DHCP server will cover
    Distribution Pool = the range of IPs that your DHCP server can hand out.

    2008R2 stops you making a reservation outside of the Distribution Pool as it doesn't make sense. When a client checks in with DHCP, the server can only hand out an IP from the Distribution Pool, if there was a reservation for an IP outside of the Pool then it couldn't hand it out anyway. Makes sense right?

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    Quote Originally Posted by browolf View Post
    Jeez, the computer labelled as #2 that i've just replaced isn't actually #2...
    The ip i'm trying to reserve is already in use but isn't an existing reservation... (checked...it's a static on that machine)

    DHCP should still allow me to create a reservation then...?
    I found that if the reservation was already active to another machine then I would struggle to be able to create a reservation using that IP address before I deleted the already active version of it .. I found that on the occasion it did let me create a reservation when the IP was already in use that when the machine I wanted to get the IP address eventually applied for it, I got a BAD_ADDRESS error in the Address Leases List.

    (does that make any sense? I'm knackered today so bear with me if I don't! lol)

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    Quote Originally Posted by sparkeh View Post
    Good explanation here: *clicky*

    Perhaps I am missing something here, but why would you want to reserve an address that outside of the distribution pool? Its not going to do anything is it?
    Oh wait I get it!

    So need to extend the start/end range in scope properties to be all possible ips. and then leave everything else as it is.
    dhcp can get things out of the already set address pool and the reservations will be happy and we can add some more?

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