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DHCP Scopes RRS feed

  • Question

  • Hi, we currently have over 100 branch offices, that are each supernet'd into their own segments of networks. e.g. SITE1 192.168.50.0/24, SITE2 192.168.80.0/27 etc etc, all different scopes depending on the location and size of the branch office. Currenly DHCP is issued from the local site router. I'm investigating the way to use IPHelpers on the routers to forward the DHCP requests to a central windows server. I want to avioid re-iping the sites. I guess then the process will be to create the indivdual scopes for each indvdual branch office on this server and point the IP Helper to the IP of the new DHCP Server. I just have two questions that I cannot find the answers to;-

    - Will bringing a second DHCP server onto the HQ network cause issues by it starting to issue IPs to the HQ network hosts that are from the station scopes?

    -How does the DHCP server know which scope to allocate IP addresses from for that specific branch office.? What is the mechanism to stop an IP from the SITE1 scope, being issued to a client on SITE2.

    Thanks in advance

    Monday, June 17, 2019 4:39 PM

All replies

  • "- Will bringing a second DHCP server onto the HQ network cause issues by it starting to issue IPs to the HQ network hosts that are from the station scopes?"

    - Yes. This is especially problematic if the secondary DHCP server is giving out addresses the original DHCP has given out. That will regularly cause some IP Duplication.

    - You define which scope is needed with the IPHelper setup. Each IPHelper is defined with the scope(s) it's associated with. Having two IPHelpers with the same scopes assigned isn't something I've seen before, but I imagine it will cause problems. Typically, IPHelpers are assigned to a specific VLAN, and there is normally only a single IPHelper per VLAN.

    Monday, June 17, 2019 4:57 PM
  • Hi Adam, thanks for the reply. The diagram below is what I am trying to achieve if possible.

    DHCP of the secondary wouldn't be giving out the same scope/addresses as the original as they are completely different ranges. My question is, what scope will be issued at the HQ?

    The Routers are Cisco and from my understanding the config is simply; ip helper-address x.x.x.x on the gateway interface. So in my case it would be; ip helper-address 192.168.0.60. So very little to define there.


    • Edited by Steve _999 Monday, June 17, 2019 7:12 PM
    Monday, June 17, 2019 7:11 PM
  • Hi,

    Just checking the current situation of your problem.
    Was your problem resolved?

    Best regards,
    Leon

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    Friday, June 21, 2019 9:48 AM
  • Hi, no, I still have the questions unanswered.
    Friday, June 21, 2019 11:09 AM
  • Hi Steve_999,

    According to your description and the configuration in the chart, it is theoretically feasible.

    Have you encountered any other problems?

    Best Regards,

    Leon


    Please remember to mark the replies as answers if they help and unmark them if they provide no help.
    If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com.

    Friday, June 28, 2019 8:18 AM