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Client can not lease IP from two different scope of DHCP

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  • Client can not lease IP from two different scope of DHCP

    Hi

    I have three scope assigned in DHCP server for three different VLAN. If I switch over workstation from one vlan to another it failed to obtain an IP from DHCP server.

    Example. if a pc is in student vlan i.e. 10.143.12.x and I want to switch over to staff vlan ie. ip of 10.143.10.x or vise versa then it fails to obtain ip from DHCP.

    My DHCP server is running ok. network is ok. ip helper address is working fine in core switch.

    What could be the trouble? please help.
    Thanks in advance
    Raihan

  • #2
    Re: Client can not lease IP from two different scope of DHCP

    Originally posted by araberuni View Post
    If I switch over workstation from one vlan to another it failed to obtain an IP from DHCP server.
    DHCP messages are broadcasted and broadcasts usually are not routed. Install a DHCP relay agent into the client subnet or configure your router to allow RFC-1531 behaviour. Oh, and make sure there is a route between vlans.

    -vP

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    • #3
      Re: Client can not lease IP from two different scope of DHCP

      I've got the same issue going on as well. Hoping someone can help out with this...

      vonPryz: The ip helper address command allows the DHCP request broadcasts to be forward to the DHCP server on a different subnet, thus allowing the request to be fulfilled..

      Our issue is that the DHCP requests are fulfilled all day long on either subnet, but when a user (not all the time, either) moves from one VLAN to the next, the PC will sometimes fail to get an IP. I still haven't put my finger around this yet, so any insight is appreciated!

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      • #4
        Re: Client can not lease IP from two different scope of DHCP

        Do you by have the Media Sense and DHCP Media Sense functions enabled or disabled?

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        • #5
          Re: Client can not lease IP from two different scope of DHCP

          Do you just move it to the new vlan and let it pick a new address ?

          TRy:
          ipconfig /release
          change vlan
          ipconfig /renew

          might help.. place i worked at we used to have to do this.
          Please do show your appreciation to those who assist you by leaving Rep Point https://www.petri.com/forums/core/im.../icon_beer.gif

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          • #6
            Re: Client can not lease IP from two different scope of DHCP

            Originally posted by tehcamel View Post
            Do you just move it to the new vlan and let it pick a new address ?

            TRy:
            ipconfig /release
            change vlan
            ipconfig /renew

            might help.. place i worked at we used to have to do this.
            I can give that shot, but I'd hate to have to tell users that they have to release their IP before undocking and going to a conference room on a different floor..

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            • #7
              Re: Client can not lease IP from two different scope of DHCP

              Originally posted by Jamsan View Post
              I'd hate to have to tell users that they have to release their IP before undocking and going to a conference room on a different floor..
              Cut down the lease time. Or add a shortcut to users' desktop that launches a script for ipconfig /renew.

              -vP

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