IP Ping of hosts (enumeration) when running as a proxy DHCP server



  • When running fog as a proxy DHCP server, that is there is another DHCP server that is providing IP addresses, enumerating systems by IP fails on every machine. This is partly caused by the primary DHCP server not reserving IP addresses for specific MAC addresses.

    It is relatively easy to get the IP by doing the following, on ubuntu at least,

    • flush the arp cache
      for arpentry in arp | grep "eth3" | cut -d " " -f1 # Obviously, set the correct interface
      do
      arp -d $arpentry
      done
    • send a ping to the broadcast address
      ping -b -c1 -w1 255.255.255.255 > /dev/null 2>&1 # Could substitute broadcast for local LAN only
    • wait for the arp table to populate
      sleep 60 # Or whatever is reasonable for the speed of your systems

    The Feature Request I am making is to have a switch to have FOG do this before trying to enumerate the hosts. Along with doing this task I would like FOG to add the determined IP address to the DB. This would of course make it so the enumeration task would not have to be modified other than adding this functionality prior to doing the enumeration.


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