k8s-nmstate-troubleshooting-dns-disconnected-env.adoc

Troubleshooting DNS connectivity issues in a disconnected environment

If you experience DNS connectivity issues when configuring nmstate in a disconnected environment, you can configure the DNS server to resolve the list of name servers for the domain root-servers.net. Alternatively, you can resolve DNS connectivity issues by configuring a custom host name and then using the hostname to perform internal networking health checks on your cluster.

Important

Ensure that the DNS server includes a name server (NS) entry for the root-servers.net zone. The DNS server does not need to forward a query to an upstream resolver, but the server must return a correct answer for the NS query.

Configuring the bind9 DNS named server

For a cluster configured to query a bind9 DNS server, you can add the root-servers.net zone to a configuration file that contains at least one NS record. For example you can use the /var/named/named.localhost as a zone file that already matches this criteria.

Procedure

1. Add the root-servers.net zone at the end of the /etc/named.conf configuration file by running the following command:

   $ cat >> /etc/named.conf <<EOF
   zone "root-servers.net" IN {
       	type master;
       	file "named.localhost";
   };
   EOF

2. Restart the named service by running the following command:

   $ systemctl restart named

3. Confirm that the root-servers.net zone is present by running the following command:

   $ journalctl -u named|grep root-servers.net

   Example output

   Jul 03 15:16:26 rhel-8-10 bash[xxxx]: zone root-servers.net/IN: loaded serial 0
   Jul 03 15:16:26 rhel-8-10 named[xxxx]: zone root-servers.net/IN: loaded serial 0

4. Verify that the DNS server can resolve the NS record for the root-servers.net domain by running the following command:

   $ host -t NS root-servers.net. 127.0.0.1

   Example output

   Using domain server:
   Name: 127.0.0.1
   Address: 127.0.0.53
   Aliases:
   root-servers.net name server root-servers.net.