RHEL 9 must configure a DNS processing mode in Network Manager.
Overview
| Finding ID | Version | Rule ID | IA Controls | Severity |
| V-257949 | RHEL-09-252040 | SV-257949r1134947_rule | CCI-000366 | medium |
| Description | ||||
| To ensure that DNS resolver settings are respected, a DNS mode in Network Manager must be configured. The following are common DNS values in NetworkManager.conf [main]: - default: NetworkManager will update /etc/resolv.conf to reflect the nameservers provided by currently active connections. - none: NetworkManager will not modify /etc/resolv.conf. Used when DNS is managed manually or by another service. - systemd-resolved: Uses systemd-resolved to manage DNS. - dnsmasq: Enables the internal dnsmasq plugin. | ||||
| STIG | Date | |||
| Red Hat Enterprise Linux 9 Security Technical Implementation Guide | 2026-02-05 | |||
Details
Check Text (C-257949r1134947_chk)
Verify that RHEL 9 has a DNS mode configured in Network Manager.
$ NetworkManager --print-config
[main]
dns=none
If the dns key under main does not exist or is not set to "default", "none", or "systemd-resolved", this is a finding.
Note: If RHEL 9 is configured to use a DNS resolver other than Network Manager, the configuration must be documented and approved by the information system security officer (ISSO).
Fix Text (F-61614r1134912_fix)
Configure NetworkManager in RHEL 9 to use a DNS mode.
In "/etc/NetworkManager/NetworkManager.conf", add the following line in the "[main]" section:
dns = <dns processing mode>
Where <dns processing mode> is default, none, or systemd-resolved.
NetworkManager must be reloaded for the change to take effect.
$ sudo systemctl reload NetworkManager