红帽全球峰会1.6. DNS forward policies in IdM
IdM supports the first and only standard BIND forward policies, as well as the none IdM-specific forward policy.
- Forward first (default)
-
The IdM BIND service forwards DNS queries to the configured forwarder. If a query fails because of a server error or timeout, BIND falls back to the recursive resolution using servers on the Internet. The
forward firstpolicy is the default policy, and it is suitable for optimizing DNS traffic. - Forward only
-
The IdM BIND service forwards DNS queries to the configured forwarder. If a query fails because of a server error or timeout, BIND returns an error to the client. The
forward onlypolicy is recommended for environments with split DNS configuration. - None (forwarding disabled)
-
DNS queries are not forwarded with the
noneforwarding policy. Disabling forwarding is only useful as a zone-specific override for global forwarding configuration. This option is the IdM equivalent of specifying an empty list of forwarders in BIND configuration.
You cannot use forwarding to combine data in IdM with data from other DNS servers. You can only forward queries for specific subzones of the primary zone in IdM DNS.
By default, the BIND service does not forward queries to another server if the queried DNS name belongs to a zone for which the IdM server is authoritative. In such a situation, if the queried DNS name cannot be found in the IdM database, the NXDOMAIN answer is returned. Forwarding is not used.
例 1.1. Example Scenario
The IdM server is authoritative for the test.example. DNS zone. BIND is configured to forward queries to the DNS server with the 192.0.2.254 IP address.
When a client sends a query for the nonexistent.test.example. DNS name, BIND detects that the IdM server is authoritative for the test.example. zone and does not forward the query to the 192.0.2.254. server. As a result, the DNS client receives the NXDomain error message, informing the user that the queried domain does not exist.
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