.. SPDX-License-Identifier: GPL-3.0-or-later Forwarding ---------- *Forwarding* configuration instructs resolver to forward cache-miss queries from clients to manually specified DNS resolvers *(upstream servers)*. In other words the *forwarding* mode does exact opposite of the default *recursive* mode because resolver in *recursive* mode automatically selects which servers to ask. Main use-cases are: - Building a tree structure of DNS resolvers to improve performance (by improving cache hit rate). - Accessing domains which are not available using recursion (e.g. if internal company servers return different answers than public ones). - Forwarding through a central DNS traffic filter. Forwarding implementation in Knot Resolver has following properties: - Answers from *upstream* servers are cached. - Answers from *upstream* servers are locally DNSSEC-validated, unless :func:`policy.STUB` is used. - Resolver automatically selects which IP address from given set of IP addresses will be used (based on performance characteristics). - Forwarding can use either unencrypted DNS protocol, or :ref:`tls-forwarding`. .. warning:: We strongly discourage use of "fake top-level domains" like ``corp.`` because these made-up domains are indistinguishable from an attack, so DNSSEC validation will prevent such domains from working. If you *really* need a variant of forwarding which does not DNSSEC-validate received data please see chapter :ref:`dns-graft`. In long-term it is better to migrate data into a legitimate, properly delegated domains which do not suffer from these security problems. Simple examples for **unencrypted** forwarding: .. code-block:: lua -- forward all traffic to specified IP addresses (selected automatically) policy.add(policy.all(policy.FORWARD({'2001:db8::1', '192.0.2.1'}))) -- forward only queries for names under domain example.com to a single IP address policy.add(policy.suffix(policy.FORWARD('192.0.2.1'), {todname('example.com.')})) To configure encrypted version please see chapter :ref:`tls-forwarding`. Forwarding is documented in depth together with rest of :ref:`mod-policy`.