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DHCP in detail?

    Question

  • Hi

    I need to know about the DHCP in detail.
    In a dhcp server configfured environment,If a dhcp server fails all the server will get apipa or until the lease time completes it will have the already released IP?
    When a dhcp lease time is configured with 8 days,when the server will request for the new ip?I mean after 7 days?
    How to configure the secondary DHCP server?
    When the primary server goes down how the node will get the ip from Secondary DHCP Server?(NO CLUSTER CONFIGURE)

    Please explain in detail all the seprate questions

    Thursday, August 18, 2011 7:20 PM

Answers

  • Hello,

    "In a dhcp server configfured environment,If a dhcp server fails all the server will get apipa or until the lease time completes it will have the already released IP?"

    After the lease expires it will use APIPA.

    "When a dhcp lease time is configured with 8 days,when the server will request for the new ip?"

    The renew process starts always after the half lease time, if a DHCP server response it will be renewed otherwise it will wait again the half from the rest of the lease, so basically now a quarter.

    "How to configure the secondary DHCP server?" and "When the primary server goes down how the node will get the ip from Secondary DHCP Server"

    Normally when you use 2 DHCP server you configure them with a 80/20 or 50/50 scope means, each server has the same scope configured but only 80 or 20 percent are activated on one and the other 20/80 are excluded, or you do the same with 50/50. http://technet.microsoft.com/en-us/library/cc754471.aspx

     

    For more networking related questions please use http://social.technet.microsoft.com/Forums/en/winserverNIS/threads as this forum is for Directory services specific questions


    Best regards Meinolf Weber Disclaimer: This posting is provided "AS IS" with no warranties or guarantees , and confers no rights.
    Thursday, August 18, 2011 7:33 PM

All replies

  • Hello,

    "In a dhcp server configfured environment,If a dhcp server fails all the server will get apipa or until the lease time completes it will have the already released IP?"

    After the lease expires it will use APIPA.

    "When a dhcp lease time is configured with 8 days,when the server will request for the new ip?"

    The renew process starts always after the half lease time, if a DHCP server response it will be renewed otherwise it will wait again the half from the rest of the lease, so basically now a quarter.

    "How to configure the secondary DHCP server?" and "When the primary server goes down how the node will get the ip from Secondary DHCP Server"

    Normally when you use 2 DHCP server you configure them with a 80/20 or 50/50 scope means, each server has the same scope configured but only 80 or 20 percent are activated on one and the other 20/80 are excluded, or you do the same with 50/50. http://technet.microsoft.com/en-us/library/cc754471.aspx

     

    For more networking related questions please use http://social.technet.microsoft.com/Forums/en/winserverNIS/threads as this forum is for Directory services specific questions


    Best regards Meinolf Weber Disclaimer: This posting is provided "AS IS" with no warranties or guarantees , and confers no rights.
    Thursday, August 18, 2011 7:33 PM
  • In addition to info already provided by Meinolf, note that the "redundant" DHCP functionality has been enhanced in Windows Server 2008 R2. Details at http://blog.studiographic.nl/?p=219

    There is, however, no "failover" functionality that you are referring to (i.e. a configuration where a secondary DHCP server would somehow "pick up" the load once the primary DHCP server fails).

    hth
    Marcin

    Thursday, August 18, 2011 8:19 PM
  • Hi,

    If the lease time is configured for 8 days, the server wont get APIPA until the lese expires.


    Renewal Process: After 50% of the lease time has passed, the client will attempt to renew the lease with the original DHCP server that it obtained the lease from using a DHCPREQUEST message. Any time the client boots and the lease is 50% or more passed, the client will attempt to renew the lease. At 87.5% of the lease completion, the client will attempt to contact any DHCP server for a new lease. If the lease expires, the client will send a request as in the initial boot when the client had no IP address. If this fails, the client TCP/IP stack will cease functioning.


    If you found this post helpful, please give it a "Helpful" vote. If it answered your question, remember to mark it as an "Answer". This posting is provided "AS IS" with no warranties and confers no rights! Always test ANY suggestion in a test environment before implementing!
    Friday, August 19, 2011 4:36 AM