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DNS_in_isolated_networks

DNS_in_isolated_networks#

Supported in IPA version 4.1 and newer

Theory#

Public internet contains root zone, handled by root servers. Recursive servers needs the root hints, list of known addresses of root servers, to be able send queries to the root servers.

In isolated you might want to have own root zone. This can be done by setting up root zone (.) as master zone on IPA DNS server. If zone is authoritative (master) root hints are not used by the IPA server.

Keep in mind that root hints have to be updated on all servers which are not authoritative for the root zone, and also on recursive clients inside the isolated network.

Example how to create root zone#

IPA DNS server: ipa.example.com.

Add root zone (.):

$ ipa dnszone-add .

Without proper delegation of zone where nameserver is located, BIND will show following error and will not load the root zone.

# journalctl -b -u named[-pkcs11]
  zone ./IN: NS 'ipa.example.com' has no address records (A or AAAA)
  zone ./IN: not loaded due to errors.

Note: IPA adds all DNS capable IPA replicas as default NS records to zone apex.

Add NS delegation for all child zones on server.

$ ipa dnszone-find --pkey-only
  Zone name: .
  Zone name:  2.0.192.in-addr.arpa.
  Zone name:  example.com.
----------------------------
Number of entries returned 3
----------------------------
$ ipa dnsforwardzone-find --pkey-only
  Zone name:  fwzone.test.
----------------------------
Number of entries returned 1
----------------------------
$ ipa dnsrecord-add . 2.0.192.in-addr.arpa. --ns-rec=ipa.example.com.
$ ipa dnsrecord-add . example.com. --ns-rec=ipa.example.com.
$ ipa dnsrecord-add . fwzone.test. --ns-rec=ipa.example.com.

Updating root hints#

This procedure updates root hints for machines which are not authoritative for the root zone. It has to be repeated every time you change IP addresses of your root servers.

In this example, the IP address 192.0.2.1 is IP address of one of your private root servers. Root hints file usually has the same format as zone file, so output from dig command can be used directly.

For BIND 9:

$ dig @192.0.2.1 . NS > /var/named/named.ca

For Unbound:

$ dig @192.0.2.1 . NS > /var/unbound/hints.ca
# add option "roothints: /var/unbound/hints.ca" to "server" section
# in /etc/unbound/unbound.conf

For Unbound utilities (drill etc.):

$ dig @192.0.2.1 . NS > /tmp/hints.ca
# use -r option for every call of the command
$ drill -r /tmp/hints.ca

DNSSEC#

Details how to use DNSSEC in isolated networks are described in article DNSSEC in isolated networks.

Category:How to Category:Draft documentation

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