projects / thirdparty / pdns.git / blame
| Commit | Line | Data |
|---|---|---|
| 20d81666 PL |
1 | Configuring Downstream Servers |
| 2 | ============================== | |
| 3 | ||
| 4 | As dnsdist is a loadbalancer and does not do any DNS resolving or serving by itself, it needs downstream servers. | |
| 5 | To add downstream servers, either include them on the command line:: | |
| 6 | ||
| 7 | dnsdist -l 130.161.252.29 -a 130.161.0.0/16 8.8.8.8 208.67.222.222 2620:0:ccc::2 2620:0:ccd::2 | |
| 8 | ||
| 9 | Or add them to the configuration file: | |
| 10 | ||
| 11 | .. code-block:: lua | |
| 12 | ||
| 13 | setLocal("130.161.252.29:53") | |
| 14 | setACL("130.161.0.0/16") | |
| 15 | newServer("8.8.8.8") | |
| 16 | newServer("208.67.222.222") | |
| 17 | newServer("2620:0:ccc::2") | |
| 18 | newServer("2620:0:0ccd::2") | |
| 19 | ||
| 20 | These two equivalent configurations give you sane load balancing using a very sensible distribution policy. | |
| 21 | Many users will simply be done with this configuration. | |
| 22 | It works as well for authoritative as for recursive servers. | |
| 23 | ||
| 24 | Healthcheck | |
| 25 | ----------- | |
| 26 | dnsdist uses a health check, sent once every second, to determine the availability of a backend server. | |
| 27 | ||
| 28 | By default, an A query for "a.root-servers.net." is sent. | |
| 29 | A different query type and target can be specified by passing, respectively, the ``checkType`` and ``checkName`` parameters to :func:`newServer`. | |
| 30 | ||
| 31 | The default behavior is to consider any valid response with an RCODE different from ServFail as valid. | |
| 32 | If the ``mustResolve`` parameter of :func:`newServer` is set to ``true``, a response will only be considered valid if its RCODE differs from NXDomain, ServFail and Refused. | |
| 33 | ||
| 34 | The number of health check failures before a server is considered down is configurable via the ``maxCheckFailures`` parameter, defaulting to 1. | |
| 35 | The CD flag can be set on the query by setting ``setCD`` to true. | |
| 36 | e.g.:: | |
| 37 | ||
| 38 | newServer({address="192.0.2.1", checkType="AAAA", checkName="a.root-servers.net.", mustResolve=true}) | |
| 44f6dbd1 RG |
39 | |
| 40 | Source address selection | |
| 41 | ------------------------ | |
| 42 | ||
| 43 | In multi-homed setups, it can be useful to be able to select the source address or the outgoing | |
| 44 | interface used by dnsdist to contact a downstream server. This can be done by using the `source` parameter:: | |
| 45 | ||
| 46 | newServer({address="192.0.2.1", source="192.0.2.127"}) | |
| 47 | newServer({address="192.0.2.1", source="eth1"}) | |
| 48 | newServer({address="192.0.2.1", source="192.0.2.127@eth1"}) | |
| 49 | ||
| 50 | The supported values for source are: | |
| 51 | - an IPv4 or IPv6 address, which must exist on the system | |
| 52 | - an interface name | |
| 53 | - an IPv4 or IPv6 address followed by '@' then an interface name | |
| 54 | ||
| 55 | Please note that specifying the interface name is only supported on system having `IP_PKTINFO`. |