Getting an IP address. With or Without DNS

The entire world now talks to itself using Transmission Control Protocol/Internet Protocol, usually abbreviated to TCP/IP.  Back in the distant past other protocols were used, NETBUEI, DECNET, and such.  They are all dead now, and TCP/IP rules.  Protocol is a set of rules for doing business.  For instance protocol for using the plain old telephone goes like this.  Lift handset. Dial 1 plus the area code for long distance,  otherwise dial just seven digits.  TCP/IP, since it is used by computers is more complex, but it deals with the same issues. 

    Part of TCP/IP is the IP address, a long string of digits that works like a telephone number.  Each computer has to have an IP address, and all the IP addresses must be unique.  Two computers may NOT have the same IP address, for obvious reasons.  In the old days, you typed the IP address into your computer.  The network administrator for your site gave out IP addresses, kept track of the ones in use, and reissued IP addresses used by old computers that were taken out of service.  As you can imagine, the Network Administrator’s job got harder and harder to do in outfits that might have thousands of desktop PC’s on the Internet.

   So they invented an automatic program running on the server, to take care of it.  Each time a desktop powers up, it asks the TCP/IP server to give it a new IP address, which it keeps until it powers down.  This server program is called Domain Name Server (DNS) or Dynamic Host Control Protocol (DHCP). Since Windows XP goes back to the bad old days of typing in IP addresses by hand, it still supports that, as well as DNS/DHCP.  You, proud computer operator get the choice of which, or both, to use.

  Normally all this complexity just works, and your computer goes on line every time you power it up.  But sometimes, for obscure and undocumented reasons,  DNS fails, your computer does not get an IP address, and you get a little message down on the task bar about “limited or no connectivity” and “IP address” .

  What to do? 

Windows Repair

Built into Windows is a repair program.  It will reset the hardware by powering it down and then up again, and then go thru the “ask-the-server-for-an-IP-address” song and dance again.  This works a good deal of the time, (but not always).  To start repair, left click on the channel’s icon down on the task bar.  This will open up a “status” window that will tell you what’s broke and offer more information tab.  Click and you will find another tab labeled “Repair”.  Click on it and hope.  It may take a while, it gives the server plenty of time to get its act together and issue an IP address.  If it doesn’t work, you will have to wait about a minute to get the bad news.  If it does work, you are home free, at least for today.

IPCONFIG

 This is essentially a manual way of doing what Repair does, with some benefits of extra information.  IPCONFIG is a DOS program, you launch it  from the DOS window.  Get the DOS window open from the Windows Run option on the Start menu.  Microsoft renamed DOS to CMD, for the Run option.  That helped everyone, a lot.  Thanks MS. 

   Like all DOS programs, IPCONFIG works off switches on its command line.  Switch /ALL makes it list out all the I/O channels (Ethernet, Wireless, etc) on your machine.  It gives the IP address (if it has one),  serial numbers, and other stuff.  Switch /RELEASE hangs up your internet connection, turns in your IP address, and takes you off line.  Switch /RENEW  does the “ask-the-server-for-an-IP-address” song and dance.  I don’t know what IPCONFIG does with no command line switches, so I don’t run it that way.  Doing IPCONFIG /RELEASE  followed by IPCONFIG /RENEW is equivalent to doing the Windows Repair. 

Alternate Configuration

 And, sometimes the server is feeling cranky and just won’t issue an IP address no matter what.  My “server” is a little 4 port Belkin wireless router, it works fine on Trusty Desktop, but just won’t issue an IP address to AntiqueLaptop. 

    You can configure the channel ask for an IP address, but if that doesn’t work, just use an IP address that you assign.  And this works on the Belkin router, why I don’t know.  To set this up, left click on the taskbar icon of your channel.  Get the status window.  Click on “Properties”  lower left.  This will display a list of all the drivers, protocols, and other bits of software that make the channel work.  Scroll thru the list and find “TCP/IP”  Click on the properties button that comes up with the selection of TCP/IP.  This accesses the properties of the TCP/IP software.   On the “General” page of TCP/IP properties, you want to check  “Obtain an IP address automatically” and “Obtain a DNS Server address automatically”. That will make your computer attempt to do the DNS song and dance.  If that dance should fail, it goes to Plan B, “Alternate Configuration”.  Check “User Configured”.  The other choice “Automatic Private IP address” is undocumented, but I believe it only works in XP Professional, which few of us have.  Below the “User Configured” are boxes for IP address, sub net mask,  Default Gateway, and Preferred DNS server.  Fill them in.

   What to Use?  For my Belkin router 192.168.2.4 works for IP Address.  Trusty Desktop, who gets his IP address from DNS (the router) is 192.168.2.2.  And he is the only other computer in the house, so I figured the .4 IP address ought to work and not conflict.  If you have a different router, different IP addresses might work.  You gotta do some snooping around.  Sub net mask is 255,255,255,0.  Both Default Gateway AND  Preferred DNS Server is 192.168.2.1, again I got that from Trusty Desktop.     

And, Lo and Behold, Antique Laptop is now back on the net.