Preparing a network node for internet access.

Check out http://www.thegeekstuff.com/2013/03/dhcp-basics/

When a system 1st comes up, it must discover its own IP and the IP of 
  the DHCP and DNS servers.

  While this information can be stored locally, it is  more commonly
    requested from a server.

  Getting an IP.
    Static IP - this is an IP assigned to a system's network card.
      Any time the system requests its IP, it should always be the same.
   
      Used for systems that need to be contacted by other systems.

    Dynamic IP - this is a random IP assigned to a system's network card
      when requested.  * must be valid for the Domain and sub-net.
 
      Like a library book, it is essentially checked out.  When the system 
      is shut down, the IP can be used by a different system on the same
      local network. * Usually a system is given 72 hrs. to reclaim IP. 

  Newer systems usually request an IP, even a static IP.
    Like the TCP/IP protocol, Ethernet has a "broadcast" frame that
      can be viewed by all nodes on the local network. 

    The client node broadcasts a packet with a broadcast Destination IP and
      the DHCP server port. The packet also contains the source-IP of 0(DHCP)
      and the client DHCP port so it can get a response.

    This packet is put in a broadcast Ethernet frame with the client 
      node's MAC@ and broadcast MAC@. Basically, a shoutout to any node
      on the local subnet listening on the dhcp server port, 67.

    If appropriate server exists on the local network and listening on the
      correct port, it will recognize the request based on the port in the 
      TCP/UDP level of the packet and return a response using the Mac@ of the 
      requester to create a response data-link frame.

    If a local DHCP service is not available, the gateway node will be 
      configured to recognize the request and re-route the IP packet to 
      appropriate IP node in the local domain with its Ethernet or equivalent 
      data-link level address.

    * under the older ARP/RARP the IP configuration service and to exist on
      the same sub-net as the querying system.
   
    The gateway system will remember the system that made the request when 
      the DHCP service returns an IP and route it back to the right local node.

    This is generally a single occurrence for a particular system when it is
      first powered up. Once it has a valid DHCP host id, it can target the 
      correct node for any additional requests.

    The DHCP server can also provide the sub-net's default gateway IP, 
      the IP[s] of available DNS servers, the sub-net mask, and other info.

From a Linux dhclient.conf file :

request subnet-mask, broadcast-address, time-offset, routers,
        domain-name, domain-name-servers, domain-search, host-name,
        dhcp6.name-servers, dhcp6.domain-search,
        netbios-name-servers, netbios-scope, interface-mtu,
        rfc3442-classless-static-routes, ntp-servers;

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