Internet Explorer must consider the requested URL to be on the intranet (local). If the computer name portion of the requested URL contains periods (such as
http://10.0.0.1), Internet Explorer assumes that the requested address exists on the Internet. And it doesn't pass any credentials automatically. Addresses without periods (such as
http://webserver) are considered to be on the intranet (local); Internet Explorer passes credentials automatically. The only exception is addresses included in the Intranet zone in Internet Explorer.
To get round this problem we can add the site to rusted lists. There are two ways
In control panel->internet options, under security the simplest way is to add it to the local intranet sites
Local Intranet_>Sites->Advanced and we can add it there
click advanced and then type the host/website address and click add
back on the security tab, click the custom level button and check the authentication is automatic logon only in intranet zone