Very quick definition: from Google:
DHCP - " (Dynamic Host Configuration Protocol) This is a protocol that lets network administrators centrally manage and automate the assignment of IP Addresses on the corporate network. When a company sets up its computer users with a connection to the Internet, an IP address must be assigned to each machine. Without DHCP, the IP address must be entered manually at each computer. DHCP lets a network administrator supervise and distribute IP addresses from a central point and automatically sends a new IP address when a computer is plugged into a different place in the network. DHCP uses the concept of a ‘lease’ or amount of time that a given IP address will be valid for a computer. Using very short leases, DHCP can dynamically reconfigure networks in which there are more computers than there are available IP addresses."

In other words, how does LAFN assign a temporary IP address every time a user logs on?

In short, we don't. Our upstream provider does. But then the question becomes: how does our wee Windows box know what IP address has been assigned to that wee box we so cherish for that brief slice of time?
Not only that, but how does that wee box of ours know how to find yahoo or google or any of several million websites across the web? That would be a DNS lookup, but again, how does the wee box get that info? Theoretically, it is through DHCP.

The Problem:

Running "ipconfig /all" from a command (cmd) shell:

• click "Start"
• click "Run"
• type "cmd" in the text field without double quotes
  (opens a DOS style window)
• type "ipconfig /all" at the command line prompt without double quotes followed by [RETURN]

when in fact it is evident that the machine must have a DHCP connection since there is an IP address allocated to the user (in this example, 69.19.248.112) and the fact that since the user can browse the internet, a DNS server must also be working.




I have been unable to get my machine to admit in ipconfig that DHCP is enabled for my assorted dialup connections.
I suspect that this is a bug in the XP release of ipconfig although I have not been able to find supporting documentation which agrees with me.

However, there are at least three other methods to confirm that DHCP is enabled.

First method (dialer properties):

• click "Start"
• hover on "Settings"
• click "Network Connections"
• rightclick on dialer of interest
• click "Properties"
• click on the "Networking" tab
• make sure that "Internet Protocol (TCP/IP)" is selected in the text field under "This connection uses the following items:"
  

• click on the "Properties" button and ensure that "Obtain an IP address automatically" and "Obtain DNS server address automatically" are selected.
  
• These settings explicitly define DHCP as being enabled.
• end of First Method to verify DHCP enabled.

Second method (Windows Services):

• click "Start"
• hover on "Settings"
• click "Control Panel"
• doubleclick on "Administrative Tools"
• doubleclick on "Services"
  
• Look for "DHCP client"
• in the "Status" column it should say "Started"
• in the "Startup Type" column it should say "Automatic"
• if the Status column says "Started", then DHCP is enabled; if the "Startup Type" says "Automatic", then DHCP is initialized at boot time.
• DO NOT CHANGE ANY SETTINGS WHEN VIEWING Administrative Services unless you really do know exactly what you are doing.
• end of Second Method to verify DHCP enabled.

Third method (ipconfig /displaydns):

• click "Start"
• click "Run"
• type "cmd" in the text field without double quotes
  (opens a DOS style window)
• type "ipconfig /displaydns" at the command line prompt without double quotes followed by "RETURN"
• you should get more than one screen indicating the assorted DNS servers which have been assigned for this dialup session. An example:
  
  
  
  
• the fact that these many DNS servers are available prove that DHCP is functioning.
• end of Third Method to verify DHCP enabled.

ipconfig is available in assorted releases in win95, 98, Me, and XP. It is strictly a command line program with the results returned in text format.

Different OS's return different available result data.

A similar program is available for win95/98/ME systems, it is called winipcfg and is generally run from a command line as well. However, it is a graphical interface and therefore slightly friendlier to folks. winipcfg is not available on XP machines.

And no, you can't just copy winipcfg over from an old box to a new box and expect it to function. I tried, it doesn't work.

This page created, first draft: September 13, 2004 0330 pdt
jtm