Please help with iRule.

Here you go:

when HTTP_REQUEST {

    set uri [string tolower [HTTP::uri]]

    if { $uri == "/" } {
        Replace 301 with 302 for a temporary redirect
        [HTTP::respond 301 Location "http://abc.mydomain.com/123/login"]
    }

}

Thank you Patrik for your quick response, i just implemented the iRule that you provided and it has resolve my problem. Your help is very much appreciated.