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Build a scalable DNS Infrastructure with Knot-DNS and FreeIPA

I've recently made a PoC at work where I build a scalable DNS Infrastructure. Please note that while the schematic includes the Windows Network, I will not go into detail with that one since this is out of scope.


Linux Datacenter (internal zones only):
FreeIPA / Red Hat IDM is a full identity management solution by Red Hat which integrates the following components:
  • - 389-DS
  • - Krb5kdc
  • - Bind Nameserver
  • - Dogtag CA
  • - Certmonger
This is a nice feature pack but I will only focus on the DNS part for now. The bind nameserver will handle internal domains and external forwarding in this setup.

Authoritative DNS (external zones only):
Knot-DNS is a high-performance authoritative DNS Server. That means, it just covers the zones itself knows about and is authoritative for. It will not forward DNS Queries to its upstream hosts.

Now, let's jump into what needs to be done to make this setup reality. I'll start by setting up the Knot-Servers.

Start by setting up the master, first install the knot server and utils:
 [archy@ns01 ~]$ yum -y install knot knot-utils
The config by default is pretty good documented. I'll configure a very basic setup, so there's not much to do. Edit the config with your favorite editor, in my case the config you see is what I found working for me.
 [archy@ns01 ~]$ vim /etc/knot/knot.conf  

 # the server configuration with the user the service is running as and the address the server listens to.  
 server:  
   rundir: "/run/knot"  
   user: knot:knot  
   listen: [ 0.0.0.0@53 ]  
 # where to log, syslog is usually a good start  
 log:  
  - target: syslog  
    any: info  
 # this is the section where to define your slaves / remote masters  
 remote:  
  - id: slave  
    address: 172.31.0.2@53  
 # ACLs allow which host is allowed to do what  
 acl:  
  - id: acl_slave  
    address: 172.31.0.2  
    action: transfer  
  - id: access_rule  
    address: [172.31.0.0/24, 172.31.100.0/24]  
    action: transfer  
  - id: deny_rule  
    address: [0.0.0.0/0]  
    action: transfer  
    deny: on  
 # Will leave essentially default for now  
 template:  
  - id: default  
    storage: "/var/lib/knot/zones"  
    file: "%s.zone"  
 # the first zone definition. All these parameters should be self explanatory.  
 zone:  
  # Master zone  
  - domain: archyslife.lan  
    storage: /var/lib/knot/zones/  
    file: archyslife.lan.zone  
    acl: [acl_slave, access_rule, deny_rule]  
    notify: slave
With the config adjusted, create the directory for the zones and define your master zone. For more info on this, check out my bind master-slave article.
 [archy@ns01 ~]$ mkdir /var/lib/knot/zones  
 [archy@ns01 ~]$ vim /var/lib/knot/zones/archyslife.lan.zone  
 @      IN     SOA ns01.archyslife.lan. ns02.archyslife.lan. (  
               2018062615  ; Serial  
               3600        ; Refresh (1 Hour)  
               3600        ; Retry (1 Hour)  
               604800      ; Expire (1 Week)  
               3600        ; Minimum (1 Hour)  
 )  
 @             NS    ns01.archyslife.lan.  
 @             NS    ns01.archyslife.lan.  
 ; A Records  
 @             A     172.31.0.1  
 @             A     172.31.0.2  
 ns01          A     172.31.0.1  
 ns02          A     172.31.0.2  
 ...
Make the knot service persistent accross reboots and start it:
 [archy@ns01 ~]$ sudo systemctl enable knot.service  
 [archy@ns01 ~]$ sudo systemctl start knot.service
With the master set up, continue with the slave setup, again by starting to install the necessary components:
 [archy@ns02 ~]$ yum -y install knot knot-utils
Next, edit the config to your liking. I ended up with this:
 [archy@ns02 ~]$ vim /etc/knot/knot.conf  

 # the server configuration with the user the service is running as and the address the server listens to.  
 server:  
   rundir: "/run/knot"  
   user: knot:knot  
   listen: [ 0.0.0.0@53 ]  
 # where to log, syslog is usually a good start  
 log:  
  - target: syslog  
   any: info  
 # this is the section where to define your slaves / remote masters  
 remote:  
  - id: master  
   address: 172.31.0.178@53  
 # ACLs allow which host is allowed to do what  
 acl:  
  - id: acl_master  
   address: 172.31.0.178  
   action: notify  
  - id: access_rule  
   address: [172.31.0.0/24, 172.31.100.0/24]  
   action: transfer  
  - id: deny_rule  
   address: [0.0.0.0/0]  
   action: transfer  
   deny: on  
 # Will leave essentially default for now  
 template:  
  - id: default  
   storage: "/var/lib/knot"  
   file: "%s.zone"  
 # the first zone definition. All these parameters should be self explanatory.  
 zone:  
   # Slave zone  
  - domain: archyslife.lan  
   storage: /var/lib/knot/zones  
   file: archyslife.lan.zone  
   acl: [acl_master, access_rule, deny_rule]  
   master: master
With the slave's config all done, create the directory for the zones and copy-paste it from your master. This is just to have this backed up on a separate host.
 [archy@ns02 ~]$ mkdir /var/lib/knot/zones  
 [archy@ns02 ~]$ vim /var/lib/knot/zones/archyslife.lan.zone  
 @      IN     SOA ns01.archyslife.lan. ns02.archyslife.lan. (  
               2018062615  ; Serial  
               3600        ; Refresh (1 Hour)  
               3600        ; Retry (1 Hour)  
               604800      ; Expire (1 Week)  
               3600        ; Minimum (1 Hour)  
 )  
 @             NS    ns01.archyslife.lan.  
 @             NS    ns01.archyslife.lan.  
 ; A Records  
 @             A     172.31.0.1  
 @             A     172.31.0.2  
 ns01          A     172.31.0.1  
 ns02          A     172.31.0.2  
 ...
Enable and restart the services to check everything comes up as expected and make the service start at reboot.
 [archy@ns02 ~]$ sudo systemctl enable knot.service  
 [archy@ns02 ~]$ sudo systemctl start knot.service
With the Authoritative DNS Section up and running, it's time to make the FreeIPA Hosts forward to the specified DNS Servers
 [archy@ipa01 ~]$ kinit  
 Password for archy@ARCHYSLIFE.LAN:  
 [archy@ipa01 ~]$ ipa dnsforwardzone-add archyslife.lan --forwarder=172.31.0.1 --forwarder=172.31.0.2 --forward-policy=only
Check back on the changes you've done and verify these are correct:
 [archy@ipa01 ~]$pa dnsforwardzone-find  
  Zone name: archyslife.lan.  
  Active zone: TRUE  
  Zone forwarders: 172.31.0.1, 172.31.0.2  
  Forward policy: only  
 ----------------------------  
 Number of entries returned 1  
 ----------------------------
Check your forwarding by running a query to your IPA Server for your Knot-DNS hosted zone:
Note: 172.31.100.250 is the address of my IPA Server
 [archy@client ~]$ nslookup ns01.archyslife.lan 172.31.100.250  
 Server:          172.31.100.250  
 Address:     172.31.100.250#53  

 Non-authoritative answer:  
 Name:     ns01.archyslife.lan  
 Address:  172.31.0.1
Everything looks good so far. If you have any troubles configuring and feel the urge to extend the config, check the manual for Knot-DNS.

Feel free to comment and / or suggest a topic.
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