2 DHCP Servers leasing same address ranges

Discussion in 'Windows Networking' started by Petri S, Sep 14, 2006.

  1. Petri S

    Petri S Guest

    Hi,

    If I have 2 DHCP servers with scopes leasing same address range, it is
    possible that other DHCP server leases address that other server has allready
    leased to some computer or are dhcp servers aware of each other so that other
    server knows that some address is already leased by another dhcp-server.
     
    Petri S, Sep 14, 2006
    #1
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  2. Petri S

    M D Guest

    Since the DHCP initialization and renewal processes are made broadcasting
    the nwtwork to search for any DHCP Server available, I thnk that any
    authorized DHCP can reply trying to assingn/renew an IP address.

    If you are you in A.D. domain, all DHCP servers must be authorized and have
    their scopes activated to be enabled to service the network

    Even though this doesn't mean they are aware of each other.

    A best practice of DHCP is the "80/20 rule": you plan to use 2 servers just
    in case 1 goes down and assign 80% of address range to the first DHCP and
    the remaining 20% to the other. Don't forget to apply exclusions to each
    other scopes! Otherwise you risk to mess up the network.

    I hope this helps you.

    Bye
    MD
     
    M D, Sep 14, 2006
    #2
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  3. Petri S

    M D Guest

    This is technically possible if the client releases the IP address (through
    a proprer shutdown or ipconfig /release) and then asks for a new IP address.
    In the DHCP renewal process instead, the DHCP Client contacts directly the
    same DHCP server that assigned its IP to get the lease renewal.

    Since the DHCP initialization process is made broadcasting
    the network to search for any DHCP Server available, any
    authorized DHCP can reply trying to assingn/renew an IP address.
    The first server that ends successfuly the DHCP discover, offer, Request and
    acknowledgement, assigns the dhcp clien a new IP address.

    This means that any DHCP server is challenged to end that process first.

    A best practice of DHCP is the "80/20 rule": you plan to use 2 servers just
    in case 1 goes down and assign 80% of address range to the first DHCP and
    the remaining 20% to the other. Don't forget to apply exclusions to each
    other scopes! Otherwise you could mess up the network.

    I hope this helps you.

    Bye
    MD
     
    M D, Sep 14, 2006
    #3
  4. Petri S

    M D Guest

    I think also that you could increase the "conflict detection" value to avoid
    a different DHCP to assign an already booked IP address. This however
    increases the network traffic and should not be taken into account as a best
    practice, I think.

    Bye

    MD
     
    M D, Sep 15, 2006
    #4
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