DHCP Copy-Machine



  • We have found the following problem:

    • if you have a dhcp-server sitting behind a pfsense with dhcp-relaying enabled, the pakets incomming to WAN going to the dhcp-server are also relayed to the configured dhcp-servers.

    example:
    wan: 192.168.2.2
    lan: 192.168.1.0/24
    dhcp-server 192.168.1.5
    dhcp-relay  192.168.3.1/ 192.168.3.2

    incoming [dhcp for 192.168.1.5] –> WAN --> dhcp-sever and also relayed to 192.168.3.1 / 192.168.3.2

    The only option to stop flooding with dhcp-request is to change the dhcrelay-options:
    dhcrelay -D -a -m discard -i eth0 eth1  192.168.3.1 192.168.3.2

    This seems to work for us, if a circuit-id is set in the incomming dhcp-paket. As the dhcprelay is started within /etc/inc/services.inc 1842 we modified that line.

    Any other ideas or thoughts on this ?


  • Rebel Alliance Global Moderator

    huh??

    So your using pfsense as a internal router/firewall and its not doing nat?



  • Yes, we are not using NAT. I think most users use NAT (SOHO).
    If you are using a firewall in a larger environment this is the case.
    Therefore it would be a good idea to make the dhcp-relay options available.


  • Rebel Alliance Global Moderator

    dhcp relay is an option..

    as to this?
    "the pakets incomming to WAN going to the dhcp-server are also relayed to the configured dhcp-servers."

    Not unless you enable relay on your pfsense wan interface..

    I would suggest you draw up your network.. If you were using pfsense as a downstream network router why would there be dhcp requests on the tranist network connecting pfsense to your upstream router?

    If your pfsense wan is 192.168.2 – how would dhcp requests for 192.168.1 network be coming into wan?

    So your relay your dhcp across your 192.168.2 transit to 192.168.2.2??  On its way to 192.168.1.5?