DHCP relay to remote server



  • I have a central office with a few remote sites.  They are all running pfsense and are all connected via OpenVPN (the central office is the server and the remote sites clients).  Currently I have a windows DHCP server running at the main office and then the DHCP server running on the pfsense at the remote offices.  This isn't ideal for administration as I have to constantly connect to the remote pfsense GUI to check on IP addresses for clients.
    I would like to implement the DHCP relay so that all of the remote sites get IP address from the main windows server.  I am aware that this maybe not be a good idea in terms of if the main office goes down, so do all the sites etc, but I am happy with this and I can always go on the individual sites and turn back on DHCP if required.

    I have tested this and can't get it to work.

    So for example say this is the topology:

    main office: 192.168.10.0/24
    DHCP server: 192.168.10.5

    remote office 1 is: 192.168.20.0/24

    vpn server routing subnet is: 192.168.200.0/24

    So what seems to happen is that when i turn on the relay and point it to the server 192.168.10.5 the requests come from the VPN subnet of 192.168.200.10 for example.  This isn't accepted by the windows DHCP server for the scope of 192.168.20.0/24 as it doesn't fall within the range.

    I tried with the "Append circuit ID and agent ID to the requests but doesn't help.

    So my question is:

    1. Does DHCP relay work over OpenVPN connections?
    2. Is there anyway to manually set the source IP address of the dhcp relay requests?
    3. Is there anyway to modify the circuit ID and agent ID manually?

    Thanks
    Kevin


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