We have two DNS servers on our domain that handle everything going to internet for clients with dynamic DNS in their settings and they work fine for most sites. However, some sites are not accessible until we put in a public DNS address manually for the client. Example: grainger.com just says it can't find the site. If i put in a public dns (such as 126.96.36.199) manually in the client settings, it goes to it. So why won't it go there with our dns servers?