DHCP Reservations VS Exclusions

Discussion in 'MCSE' started by mark, Nov 26, 2003.

  1. mark

    mark Guest

    I understand that you create an Exclusion Range in DHCP
    for say Static addresses or to exclude other subnet
    addresses from dynamically being assigned.
    But when or why do you create Reservations in DHCP to
    reserve what ??
    And when do you know which one to use??
    mark, Nov 26, 2003
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  2. mark

    cadman Guest

    Use reservations when you want the same client (mac address of the nic) to
    always get the same ip address. Sort of like a static address handed out
    from the DHCP Server. That way you will always know the address of that
    client, since it has an ip address reservation.
    cadman, Nov 26, 2003
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  3. mark

    no one Guest

    Let's say you set up a network printer with an internal
    print server. When you first put it online, it will pick
    up a dynamically assigned address from DHCP. Generally,
    when I designate a DHCP pool of assignable addresses, I
    exclude the first 20 or 25 for static assignments
    (servers, print servers, routers, etc). But I forgot to
    statically assign the one for the new network printer.
    So I would set up an exclusion for that IP address in my
    address range so DHCP would not assign it to another
    client. This effectively created an "exclusion" for that
    IP address. Alternatively, I could have gone in and
    statically assigned the print server an IP address in the
    range below 20 or 25. A "REAL" reservation would be set
    up if you set up your assignable addresses as x.y.z.1-
    254/24 and then create reservations for x.y.z.1-25. Same
    difference. You have defined the entire class c address
    as an assignable pool and then reserved the first 25 for
    static assignment. An exclusion is used when you want to
    exclude an address within the assignable pool for
    instances like the network printer above. Clear as mud?
    no one, Nov 26, 2003
  4. mark

    McGlinchey Guest

    Wow - there's finally something I can help with!!

    We use exclusions at FEMA like "no one" said - we exclude
    a range of IP addresses for servers, routers, etc. and for
    printers that we'll set up with IP printing. If we need
    an IP address for one of those purposes we'll pull from
    that range.

    We also have applications that are partially secured by IP
    address - only a specific user can log into the server
    from a specific IP addressed machine and gain access. For
    those individuals, we reserve an IP address specifically
    for their NIC card's MAC address and manually configure
    TCP/IP on their machine.

    Hopefully that gives you a "real world" example...good
    McGlinchey, Nov 26, 2003
  5. mark

    mark Guest

    So Reservations are used if you want to always assign the
    same address/mac. Used for example printers, Servers, Etc.
    An Exclusion is a range of addresses used for blocks of
    addresses for example a pool of DHCP addresses that are
    being assigned from a different source or static
    IPaddresses. If you had all your servers say
    to I would use an exclusion. And if I had
    two print servers say and I can
    Reserve these using the MAC addresses of the device.
    One last thing can you make a reservation on a different
    subnet ? I notice a check box for Supported types
    Both/DHCP or BootP. What is that for?
    mark, Nov 26, 2003
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