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diff --git a/docs/configuration/service/dns.rst b/docs/configuration/service/dns.rst new file mode 100644 index 00000000..f332c55c --- /dev/null +++ b/docs/configuration/service/dns.rst @@ -0,0 +1,313 @@ +.. _dns-forwarding: + +############## +DNS Forwarding +############## + +Configuration +============= + +VyOS provides DNS infrastructure for small networks. It is designed to be +lightweight and have a small footprint, suitable for resource constrained +routers and firewalls, for this we utilize PowerDNS recursor. + +The VyOS DNS forwarder does not require an upstream DNS server. It can serve as a +full recursive DNS server - but it can also forward queries to configurable +upstream DNS servers. By not configuring any upstream DNS servers you also +avoid to be tracked by the provider of your upstream DNS server. + +.. cfgcmd:: set service dns forwarding system + + Forward incoming DNS queries to the DNS servers configured under the ``system + name-server`` nodes. + +.. cfgcmd:: set service dns forwarding name-server <address> + + Send all DNS queries to the IPv4/IPv6 DNS server specified under `<address>`. + You can configure multiple nameservers here. + +.. cfgcmd:: set service dns forwarding domain <domain-name> server <address> + + Forward received queries for a particular domain (specified via `domain-name`) + to a given name-server. Multiple nameservers can be specified. You can use + this feature for a DNS split-horizon configuration. + + .. note:: This also works for reverse-lookup zones (``18.172.in-addr.arpa``). + +.. cfgcmd:: set service dns forwarding allow-from <network> + + Given the fact that open DNS recursors could be used on DDOS amplification + attacts, you must configure the networks which are allowed to use this + recursor. A network of ``0.0.0.0/0`` or ``::/0`` would allow all IPv4 and + IPv6 networks to query this server. This is on general a bad idea. + +.. cfgcmd:: set service dns forwarding dnssec <off | process-no-validate | process | log-fail | validate> + + The PowerDNS Recursor has 5 different levels of DNSSEC processing, which can + be set with the dnssec setting. In order from least to most processing, these + are: + + * **off** In this mode, no DNSSEC processing takes place. The recursor will + not set the DNSSEC OK (DO) bit in the outgoing queries and will ignore the + DO and AD bits in queries. + + * **process-no-validate** In this mode the Recursor acts as a "security + aware, non-validating" nameserver, meaning it will set the DO-bit on + outgoing queries and will provide DNSSEC related RRsets (NSEC, RRSIG) to + clients that ask for them (by means of a DO-bit in the query), except for + zones provided through the auth-zones setting. It will not do any + validation in this mode, not even when requested by the client. + + * **process** When dnssec is set to process the behaviour is similar to + process-no-validate. However, the recursor will try to validate the data + if at least one of the DO or AD bits is set in the query; in that case, + it will set the AD-bit in the response when the data is validated + successfully, or send SERVFAIL when the validation comes up bogus. + + * **log-fail** In this mode, the recursor will attempt to validate all data + it retrieves from authoritative servers, regardless of the client's DNSSEC + desires, and will log the validation result. This mode can be used to + determine the extra load and amount of possibly bogus answers before + turning on full-blown validation. Responses to client queries are the same + as with process. + + * **validate** The highest mode of DNSSEC processing. In this mode, all + queries will be validated and will be answered with a SERVFAIL in case of + bogus data, regardless of the client's request. + + .. note:: The famous UNIX/Linux ``dig`` tool sets the AD-bit in the query. + This might lead to unexpected query results when testing. Set ``+noad`` + on the ``dig`` commandline when this is the case. + + .. note:: The ``CD``-bit is honored correctly for process and validate. For + log-fail, failures will be logged too. + +.. cfgcmd:: set service dns forwarding ignore-hosts-file + + Do not use local ``/etc/hosts`` file in name resolution. VyOS DHCP server + will use this file to add resolvers to assigned addresses. + +.. cfgcmd:: set service dns forwarding max-cache-entries + + Maximum number of DNS cache entries. 1 million per CPU core will generally + suffice for most installations. + +.. cfgcmd:: set service dns forwarding negative-ttl + + A query for which there is authoritatively no answer is cached to quickly + deny a record's existence later on, without putting a heavy load on the + remote server. In practice, caches can become saturated with hundreds of + thousands of hosts which are tried only once. This setting, which defaults + to 3600 seconds, puts a maximum on the amount of time negative entries are + cached. + +.. cfgcmd:: set service dns forwarding listen-address + + The local IPv4 or IPv6 addresses to bind the DNS forwarder to. The forwarder will listen on this address for + incoming connections. + +Example +======= + +A VyOS router with two interfaces - eth0 (WAN) and eth1 (LAN) - is required to implement a split-horizon DNS configuration for example.com. + +In this scenario: + +* All DNS requests for example.com must be forwarded to a DNS server at 192.0.2.254 + and 2001:db8:cafe::1 +* All other DNS requests will be forwarded to a different set of DNS servers at 192.0.2.1, + 192.0.2.2, 2001:db8::1:ffff and 2001:db8::2:ffff +* The VyOS DNS forwarder will only listen for requests on the eth1 (LAN) interface addresses - 192.168.1.254 + for IPv4 and 2001:db8::ffff for IPv6 +* The VyOS DNS forwarder will only accept lookup requests from the LAN subnets - 192.168.1.0/24 and 2001:db8::/64 + +.. code-block:: none + + set service dns forwarding domain example.com server 192.0.2.254 + set service dns forwarding domain example.com server 2001:db8:cafe::1 + set service dns forwarding name-server 192.0.2.1 + set service dns forwarding name-server 192.0.2.2 + set service dns forwarding name-server 2001:db8::1:ffff + set service dns forwarding name-server 2001:db8::2:ffff + set service dns forwarding listen-address 192.168.1.254 + set service dns forwarding listen-address 2001:db8::ffff + set service dns forwarding allow-from 192.168.1.0/24 + set service dns forwarding allow-from 2001:db8::/64 + +Operation +========= + +.. opcmd:: reset dns forwarding <all | domain> + + Resets the local DNS forwarding cache database. You can reset the cache for all + entries or only for entries to a specific domain. + +.. opcmd:: restart dns forwarding + + Restarts the DNS recursor process. This also invalidates the local DNS forwarding cache. + + +.. _dynamic-dns: + +########### +Dynamic DNS +########### + +VyOS is able to update a remote DNS record when an interface gets a new IP +address. In order to do so, VyOS includes ddclient_, a Perl script written for +this only one purpose. + +ddclient_ uses two methods to update a DNS record. The first one will send +updates directly to the DNS daemon, in compliance with :rfc:`2136`. The second +one involves a third party service, like DynDNS.com or any other similar +website. This method uses HTTP requests to transmit the new IP address. You +can configure both in VyOS. + +Configuration +============= + +:rfc:`2136` Based +----------------- + +.. cfgcmd:: set service dns dynamic interface <interface> rfc2136 <service-name> + + Create new :rfc:`2136` DNS update configuration which will update the IP + address assigned to `<interface>` on the service you configured under + `<service-name>`. + +.. cfgcmd:: set service dns dynamic interface <interface> rfc2136 <service-name> key <keyfile> + + File identified by `<keyfile>` containing the secret RNDC key shared with + remote DNS server. + +.. cfgcmd:: set service dns dynamic interface <interface> rfc2136 <service-name> server <server> + + Configure the DNS `<server>` IP/FQDN used when updating this dynamic + assignment. + +.. cfgcmd:: set service dns dynamic interface <interface> rfc2136 <service-name> zone <zone> + + Configure DNS `<zone>` to be updated. + +.. cfgcmd:: set service dns dynamic interface <interface> rfc2136 <service-name> record <record> + + Configure DNS `<record>` which should be updated. This can be set multiple + times. + +.. cfgcmd:: set service dns dynamic interface <interface> rfc2136 <service-name> ttl <ttl> + + Configure optional TTL value on the given resource record. This defualts to + 600 seconds. + +Example +^^^^^^^ + +* Register DNS record ``example.vyos.io`` on DNS server ``ns1.vyos.io`` +* Use auth key file at ``/config/auth/my.key`` +* Set TTL to 300 seconds + +.. code-block:: none + + vyos@vyos# show service dns dynamic + interface eth0.7 { + rfc2136 VyOS-DNS { + key /config/auth/my.key + record example.vyos.io + server ns1.vyos.io + ttl 300 + zone vyos.io + } + } + +This will render the following ddclient_ configuration entry: + +.. code-block:: none + + # + # ddclient configuration for interface "eth0.7": + # + use=if, if=eth0.7 + + # RFC2136 dynamic DNS configuration for example.vyos.io.vyos.io + server=ns1.vyos.io + protocol=nsupdate + password=/config/auth/my.key + ttl=300 + zone=vyos.io + example.vyos.io + +.. note:: You can also keep different DNS zone updated. Just create a new + config node: ``set service dns dynamic interface <interface> rfc2136 + <other-service-name>`` + +HTTP based services +------------------- + +VyOS is also able to use any service relying on protocols supported by ddclient. + +To use such a service, one must define a login, password, one or multiple +hostnames, protocol and server. + +.. cfgcmd:: set service dns dynamic interface <interface> service <service> host-name <hostname> + + Setup the dynamic DNS hostname `<hostname>` associated with the DynDNS + provider identified by `<service>` when the IP address on interface + `<interface>` changes. + +.. cfgcmd:: set service dns dynamic interface <interface> service <service> login <username> + + Configure `<username>` used when authenticating the update request for + DynDNS service identified by `<service>`. + For Namecheap, set the <domain> you wish to update. + +.. cfgcmd:: set service dns dynamic interface <interface> service <service> password <password> + + Configure `<password>` used when authenticating the update request for + DynDNS service identified by `<service>`. + +.. cfgcmd:: set service dns dynamic interface <interface> service <service> protocol <protocol> + + When a ``custom`` DynDNS provider is used the protocol used for communicating + to the provider must be specified under `<protocol>`. See the embedded + completion helper for available protocols. + +.. cfgcmd:: set service dns dynamic interface <interface> service <service> server <server> + + When a ``custom`` DynDNS provider is used the `<server>` where update + requests are being sent to must be specified. + +Example: +^^^^^^^^ + +Use DynDNS as your preferred provider: + +.. code-block:: none + + set service dns dynamic interface eth0 service dyndns + set service dns dynamic interface eth0 service dyndns login my-login + set service dns dynamic interface eth0 service dyndns password my-password + set service dns dynamic interface eth0 service dyndns host-name my-dyndns-hostname + +.. note:: Multiple services can be used per interface. Just specify as many + serives per interface as you like! + +Running Behind NAT +------------------ + +By default, ddclient_ will update a dynamic dns record using the IP address +directly attached to the interface. If your VyOS instance is behind NAT, your +record will be updated to point to your internal IP. + +ddclient_ has another way to determine the WAN IP address. This is controlled +by: + +.. cfgcmd:: set service dns dynamic interface <interface> use-web url <url> + + Use configured `<url>` to determine your IP address. ddclient_ will load + `<url>` and tries to extract your IP address from the response. + +.. cfgcmd:: set service dns dynamic interface <interface> use-web skip <pattern> + + ddclient_ will skip any address located before the string set in `<pattern>`. + +.. _ddclient: https://github.com/ddclient/ddclient |