RHEL 9 must not enable IPv4 packet forwarding unless the system is a router.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-257970	RHEL-09-253075	SV-257970r943001_rule		Medium

Description
Routing protocol daemons are typically used on routers to exchange network topology information with other routers. If this capability is used when not required, system network information may be unnecessarily transmitted across the network.

STIG	Date
Red Hat Enterprise Linux 9 Security Technical Implementation Guide	2023-12-01

Details

Check Text ( C-61711r943000_chk )

Verify RHEL 9 is not performing IPv4 packet forwarding, unless the system is a router. Check that IPv4 forwarding is disabled using the following command: $ sudo sysctl net.ipv4.conf.all.forwarding net.ipv4.conf.all.forwarding = 0 If the IPv4 forwarding value is not "0" and is not documented with the information system security officer (ISSO) as an operational requirement, this is a finding. Check that the configuration files are present to enable this network parameter. $ sudo (/usr/lib/systemd/systemd-sysctl --cat-config; cat /etc/sysctl.conf) | egrep -v '^(#|$)' | grep net.ipv4.conf.all.forwarding | tail -1 net.ipv4.conf.all.forwarding = 0 If "net.ipv4.conf.all.forwarding" is not set to "0" and is not documented with the ISSO as an operational requirement or is missing, this is a finding.

Fix Text (F-61635r925896_fix)
Configure RHEL 9 to not allow IPv4 packet forwarding, unless the system is a router. Add or edit the following line in a single system configuration file, in the "/etc/sysctl.d/" directory: net.ipv4.conf.all.forwarding = 0 Load settings from all system configuration files with the following command: $ sudo sysctl --system