Redirected you too many times error

Question

using asp.net webforms,iis 7.5
this error occurs on specific ip's after 5,6 days.currently its working everywhere but shows this error on some specific ip's.Tried reseting browsers,but seems there is something wrong in my code.Also another application hosted on same ip with different port is also having same issue.

Error:
The 111.111.111 page isn’t working

111.111.111.111 redirected you too many times. Try clearing your cookies. ERR_TOO_MANY_REDIRECTS

my global.asax:

if (HttpContext.Current.Request.Url.ToString().ToLower().Contains("http://111.111.111.111/Default.aspx"))
{  
    HttpContext.Current.Response.Status = "301 Moved Permanently";
    HttpContext.Current.Response.AddHeader("Location", Request.Url.ToString().ToLower().Replace("http://111.111.111.111", "http://www.abcd.com"));
}