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February 09, 2000 12:00 AM

What is the Microsoft Loopback adapter and why do I need it for SQL Server?

Windows IT Pro
InstantDoc ID #14400
Rating: (12)

A. SQL Server is dependent on network functionality - even for the set-up routines. Specifically it needs to use named-pipe/mailslot functionality on NT machines. These usually require a network card to be present. If you don't have a network card then go to control panel/networks, choose add adapter and then add the Microsoft loopback adapter - which is just a dummy driver, no hardware involved. This needs to have working network protocol(s) bound to it. Let whichever protocols you have use default parameters, EXCEPT for tcp-ip. If you are using this then do NOT specify dhcp assigned address, use 192.168.1.1 as the IP address and 255.255.255.0 as the subnet mask. This is a standard RFC1918 non-routed IP address so shouldn't clash with any dial-up address you may be given by an ISP.

If the server service does not start after installing the loopback adapter and you get the following message in the event log, then you need to re-install your *NT* service pack to synchronise your NT networking files. "The server service terminated with the following error: Not enough server storage is available to process this command"

One way of testing that the named-pipes functionality works is to run the makepipe and readpipe utilities that come with SQL Server. Run makepipe in one command window. Then run readpipe in another. If these work (i.e. the readpipe connects to makepipe and closes it down) then it is a good indication that networking functionality is ok.

For Win9x machines you don't need a loopback adapter to install but you do need to have the "MS Network Family Driver" installed and the default network client.


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Comments
  • unix_is_better_than_win32
    6 years ago
    Jun 21, 2006

    Look... You'll notice that this magazine is called "Windows IT *PRO*", not "Windows IT Beginner". Asking a question about an article is fine, but the fact that you have the nerve to be *indignant* about the fact that you don't understand a technical definition of a technical concept written for "Windows IT **Professionals**" is pathetic. Not knowing what a loopback interface is doesn't make you an idiot, not knowing how to ask without being a jerk makes you an idiot. Now that we've gotten that out of the way, here we go.

    Definitions-
    Network Card: A physical card in the computer connected to a network.
    Network Interface: Simply the label your computers uses for the card&the network settings for the card.
    Let's say you have just put in a second network card in the pci0 in your computer. Windows will say "Oh look, new hardware... alright it's a network card. Ok, I've got the drivers right here. Let's call this one "Local Area Connection 2". And then if you right click on local area connection 2 in your network connections thing, and select properties, you'll see all of the settings that windows applied to it.
    A network interface is what your computer uses to reach a network, through a network card.

    Loopback is a SPECIAL network interface. Instead of connecting the computer to a network, it just sends the data back to the computer.

    You have a web server, from the server you wanted to view the webpage, you wouldn't need a network card for that. Just point your webbrowser at the "Loopback address" (127.0.0.1) and it will make your browser *think* it's going out over the net and getting a webpage, but it's really just going to a fake network interface which is sending the info right back at you. Just like if you have a DB srver on your comp... to cnnct, you need a db client whch expects a network cnnctn. If access it frm the same machine, just point the client at 127.0.0.1 & it will think that it is connecting to a network, but it's connecting to itself!

  • Anonymous User
    7 years ago
    Aug 28, 2005

    I'm as well a novice in this area of VPN. i only stumble on it while trying to install Oracle10g on which i have dhcp as the source of my IP address given through my ISP connection. I'll like to know the reason why I need to configure Microsoft Loopback adapter as my primary network adapter and what will be the efect of this configuration on my existing adapters.Thankx

  • Anonymous User
    7 years ago
    Aug 12, 2005

    So, still no real clear answer to all those asking for it in plain English - isn't it just another way for MS to snoop?

  • Anonymous User
    7 years ago
    Apr 23, 2005

    The best reason for using the loopback adapter is when you have not got any physical network adapter installed in your PC and despite that you still want to use i.e. TCP/IP protocol for accessing your MS SQL Server running on your machine, for example. Bron.

  • Anonymous User
    7 years ago
    Apr 12, 2005

    loopback adapter is used for running a virtual machine. this has become a practice now to use virtual machines for testing and configuring the solutions. and yeas virtual machines can be treated as a separte machine running on LAN

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