asp C# login problem

I am looking for a way to authenticate at multiple servers at the same time. One login for multiple sites ( a.com , b.com, c.com )

All the servers are on one network. Ldap authentication

Thanks for the help

Single sign on. This is what you are looking for.

There should be lot of examples on net. see one of them below

 http://aspalliance.com/1545  

LDAP example:

http://www.codeproject.com/kb/dotnet/LDAPSSO.aspx

Are you trying to have a common authentication across multiple sites? If so, you need to share authentication cookies across multiple ASP.NET web sites. You use the same machineKey in your web.config files.

When you have logged in to one web site, navigate to second web site in the same browser session should identify you as logged. Put a asp:LoginName control and you will see the user name.

For further details see this

One way is by making cookies available across domains as described in this article.

Better and more detailed article regarding ASP.NET here.