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Hi All, i could not find the answer, so if someone has experience please enlighten me. If I have 2 DHCPs. let say i load it 80/20. So first DHCP ...
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  1. #1
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    How 2 DHCP servers working on same network?


    Hi All,

    i could not find the answer, so if someone has experience please enlighten me.

    If I have 2 DHCPs. let say i load it 80/20.
    So first DHCP server got IP pool 1 - 200
    second DHCP server got the IP 200-254

    I know that client will do the braodcast, then whichever answer first, will be its DHCP server.


    But when the first DHCP has leased all the IP, and a new client connect/request IP from the 1st DHCP, would the client then go to the 2nd DHCP?? or the client will not get any IP.


    Thanks,

  2. #2
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    Good question

    Ok,

    1. the first question I have is what type of network do you have, is it based on vlans or it is a flat network
    2. The DHCP servers you are using are they linux or windows servers
    3. Why are you setting up the DHCP servers in this way, just curious, so it will help me find the right answer
    4. Are you doing this for redundancy or just failover?

    Please advise.

    Todd

  3. #3
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    When a client requests a DHCP connection, it waits and collects information from the responses (within a period time) and picks one and tells that server that it accepts the connection. The server tells it if it has not given that address to another or not. If the address is okay by the server, the client queries the network to see if anyone is already using the address if not it will use the address.


    On a linux system, it is really easy to include a "black list" of do not use these DHCP servers.

  4. #4
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    Response to explanation

    No, I do understand the process, I am just curious about why he wants to separate the two DHCP servers, is there a purpose behind why he is going down this path.

    It would help me to understand. I do agree with your sentiments earlier but the problem remains as to the purpose, you can place Linux or Windows DHCP servers in place to provide him what he needs but what type of network are these servers on (carved up using vlans) and does he have ip helper items placed in the router to allow the traffic to traverse the network, is this going to be used for a wireless implementation.

    The process will work but it sounds like he wants to balance the load of the various devices or use them as a failover scenario, that will help me address how to setup the DHCP servers.

    But if the explanation is fine for you, then so be it, some good reading would be to go to this site:

    Linux Tutorial - Linux DHCP Server Configuration

    https://help.ubuntu.com/community/dhcp3-server

    It is dependent on the type of network you are on, if you want to configure two DHCP servers or use one with dual interfaces for different networks.

    I think the article above addresses your question, so yes you can configure both on the same network to load balance the requests, however, the reasoning why you do it still remains in question.

    Todd

  5. #5
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    My best guess is he wants to have a fail-over scenario.

    Googling 'DHCP failover' came with a nice setup: http://yourlinuxguy.com/?p=269

    have fun...

  6. #6
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    I guess you could find out the answer by making the first pool very small, then it would be obvious if it worked or you had a problem. Good luck.

  7. #7
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    Hi. By its nature, your cannot have 2 DHCP servers on the same network. You may have a main+backup setup following the guide given. You may also have a secondary DHCP, which is only a kind of proxy to the first one. When I studied DHCP at the university, I was said "you cannot have 2 DHCP on the same network".

  8. #8
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    The standard does not restrict a network (or subnet) to only one DHCP it is a practical aspect that drives a single DHCP server.

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