Quickstart Guide¶
This guide gives an overview of dnsdist features and operations.
Running in the Foreground¶
After installing dnsdist, the quickest way to start experimenting is launching it on the foreground with:
dnsdist -l 127.0.0.1:5300 9.9.9.9 2620:fe::fe 2620:fe::9
This will make dnsdist listen on IP address 127.0.0.1, port 5300 and forward all queries to the three listed IP addresses, with a sensible balancing policy.
dnsdist Console and Configuration¶
Here is more complete configuration, save it to dnsdist.conf:
newServer({address="2001:db8::1", qps=1})
newServer({address="2001:db8::2", qps=1})
newServer({address="[2001:db8::3]:5300", qps=10})
newServer({address="2001:db8::4", name="dns1", qps=10})
newServer("192.0.2.1")
setServerPolicy(firstAvailable) -- first server within its QPS limit
The newServer() function is used to add a backend server to the configuration.
Now run dnsdist again, reading this configuration:
$ dnsdist -C dnsdist.conf --local=0.0.0.0:5300
Marking downstream [2001:db8::1]:53 as 'up'
Marking downstream [2001:db8::2]:53 as 'up'
Marking downstream [2001:db8::3]:5300 as 'up'
Marking downstream [2001:db8::4]:53 as 'up'
Marking downstream 192.0.2.1.:53 as 'up'
Listening on 0.0.0.0:5300
>
You can now send queries to port 5300, and get answers:
$ dig -t aaaa powerdns.com @127.0.0.1 -p 5300 +short +nocookie
2001:888:2000:1d::2
Note that dnsdist dropped us in a prompt above, where we can get some statistics:
> showServers()
# Address State Qps Qlim Ord Wt Queries Drops Drate Lat Pools
0 [2001:db8::1]:53 up 0.0 1 1 1 1 0 0.0 0.0
1 [2001:db8::2]:53 up 0.0 1 1 1 0 0 0.0 0.0
2 [2001:db8::3]:5300 up 0.0 10 1 1 0 0 0.0 0.0
3 [2001:db8::4]:53 up 0.0 10 1 1 0 0 0.0 0.0
4 192.0.2.1:53 up 0.0 0 1 1 0 0 0.0 0.0
All 0.0 1 0
showServers() is usually one of the first commands you will use when logging into the console. More advanced topics are covered in Working with the dnsdist Console.
Here we also see our configuration. 5 downstream servers have been configured, of which the first 4 have a QPS limit (of 1, 1, 10 and 10 queries per second, respectively).
The final server has no limit, which we can easily test:
$ for a in {0..1000}; do dig powerdns.com @127.0.0.1 -p 5300 +noall +nocookie > /dev/null; done
> showServers()
# Address State Qps Qlim Ord Wt Queries Drops Drate Lat Pools
0 [2001:db8::1]:53 up 1.0 1 1 1 7 0 0.0 1.6
1 [2001:db8::2]:53 up 1.0 1 1 1 6 0 0.0 0.6
2 [2001:db8::3]:5300 up 10.3 10 1 1 64 0 0.0 2.4
3 [2001:db8::4]:53 up 10.3 10 1 1 63 0 0.0 2.4
4 192.0.2.1:53 up 125.8 0 1 1 671 0 0.0 0.4
All 145.0 811 0
Note that the first 4 servers were all limited to near their configured QPS, and that our final server was taking up most of the traffic. No queries were dropped, and all servers remain up.
Changing Server Settings¶
The servers from showServers() are numbered, getServer() is used to get this Server object to manipulate it.
To force a server down, try Server:setDown():
> getServer(0):setDown()
> showServers()
# Address State Qps Qlim Ord Wt Queries Drops Drate Lat Pools
0 [2001:db8::1]:53 DOWN 0.0 1 1 1 8 0 0.0 0.0
...
The DOWN in all caps means it was forced down.
A lower case down would’ve meant that dnsdist itself had concluded the server was down.
Similarly, Server:setUp() forces a server to be up, and Server:setAuto() returns it to the default availability-probing.
To change the QPS for a server, use Server:setQPS():
> getServer(0):setQPS(1000)
Restricting Access¶
By default, dnsdist listens on 127.0.0.1 (not ::1!), port 53.
To listen on a different address, use the -l command line option (useful for testing in the foreground), or use setLocal() and addLocal() in the configuration file:
setLocal('192.0.2.53') -- Listen on 192.0.2.53, port 53
addLocal('[::1]:5300') -- Also listen on ::1, port 5300
Before packets are processed they have to pass the ACL, which helpfully defaults to RFC 1918 private IP space. This prevents us from easily becoming an open DNS resolver.
Adding network ranges to the ACL is done with the setACL() and addACL() functions:
setACL({'192.0.2.0/28', '2001:db8:1::/56'}) -- Set the ACL to only allow these subnets
addACL('2001:db8:2::/56') -- Add this subnet to the existing ACL
Securing the path to the backend¶
dnsdist has always been designed as a load-balancer placed in front of authoritative or recursive servers, assuming that the network path between dnsdist and these servers is trusted.
If dnsdist is instead intended to be deployed in such a way that the path to its backend is not secure, the UDP protocol should not be used, and ‘TCP-only’, DNS over TLS and DNS over HTTPS protocols used instead, as supported since 1.7.0.
For more details, please look at the Configuring Downstream Servers guide.
More Information¶
Following this quickstart guide allowed you to set up a basic balancing dnsdist instance. However, dnsdist is much more powerful. See the Guides and/or the Advanced Topics sections on how to shape, shut and otherwise manipulate DNS traffic.