@Doc-J Ignore? Sites not listed in a DNS would generate an error message to tell you there is a problem. If you want to actually block a site via DNS, you'd have to return an address that isn't actually allowed, such as 0.0.0.0 - it should just ignore that, I think.
General redirects to a different domain - sites on the internet can change providers, if the new domain is legitimate the browser should follow redirects.. If you mean redirects from your network to an external site, that would be your DNS.
