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

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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.


End of Article



Reader Comments
Hello there,

I am not a stupid person & I do build, install & tech support computers. But I am not understanding what the purpose of the "Microsoft Loopback Adapter" is even after reasding this article?? Can you please help me a little slower......

Thank you

craig April 25, 2003


can i use loopback adapter in any lan connection?

subhankar April 09, 2004


Curently a student and having a hard time understanding the computer language. Have excellent teacher but he teaches as if we should "ALREADY" know the info and more often than not i have to write down what he says then look it up so i could understand what the lecture was. Pretty much the same way in reading your article. So could you please explain your articles in "gradeschool computer language" so that those of us could still understand what is meant. Still have no clue what a loopback plug or an analog loopback adapter is...Help test in one week....

renee April 26, 2004


PLEASE EXPLAIN IN SHORT THE NEED FOR LOOPBACK ADAPTER.........

Anonymous User February 08, 2005


RALLY REALLY COULD NOT UNDERSTAD ANYTHING, PLEASE BE MORE GENERIC AS MANY READERES WON'T BE ABLE TO CONCEIVE THE TERMS. PLS B GENERIC AND ILLUSTRATE IN SHORT..........

Anonymous User February 09, 2005


Need Better way of understanding for Dummies

Anonymous User February 23, 2005 (Article Rating: )


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

Anonymous User April 12, 2005 (Article Rating: )


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 April 23, 2005 (Article Rating: )


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 August 12, 2005 (Article Rating: )


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 August 28, 2005 (Article Rating: )


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