OL 8 must not accept router advertisements on all IPv6 interfaces.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-248884	SRG-OS-000480-GPOS-00227	OL08-00-040261	SV-248884r1156637_rule	2025-12-08	2

Description
Routing protocol daemons are typically used on routers to exchange network topology information with other routers. If this software is used when not required, system network information may be unnecessarily transmitted across the network. An illicit router advertisement message could result in a man-in-the-middle attack. The sysctl --system command will load settings from all system configuration files. All configuration files are sorted by their filename in lexicographical order, regardless of the directories in which they reside. If multiple files specify the same option, the entry in the file with the lexicographically latest name will take precedence. Files are read from directories in the following list from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. /etc/sysctl.d/.conf /run/sysctl.d/.conf /usr/local/lib/sysctl.d/.conf /usr/lib/sysctl.d/.conf /lib/sysctl.d/*.conf /etc/sysctl.conf

Description

Routing protocol daemons are typically used on routers to exchange network topology information with other routers. If this software is used when not required, system network information may be unnecessarily transmitted across the network. An illicit router advertisement message could result in a man-in-the-middle attack. The sysctl --system command will load settings from all system configuration files. All configuration files are sorted by their filename in lexicographical order, regardless of the directories in which they reside. If multiple files specify the same option, the entry in the file with the lexicographically latest name will take precedence. Files are read from directories in the following list from top to bottom. Once a file of a given filename is loaded, any file of the same name in subsequent directories is ignored. /etc/sysctl.d/*.conf /run/sysctl.d/*.conf /usr/local/lib/sysctl.d/*.conf /usr/lib/sysctl.d/*.conf /lib/sysctl.d/*.conf /etc/sysctl.conf

ℹ️ Check
Note: If IPv6 is disabled on the system, this requirement is Not Applicable. Verify OL 8 does not accept router advertisements on all IPv6 interfaces, unless the system is a router. Determine if router advertisements are not accepted by using the following command: $ sysctl net.ipv6.conf.all.accept_ra net.ipv6.conf.all.accept_ra = 0 If the "accept_ra" value is not "0" and is not documented with the information system security officer (ISSO) as an operational requirement, this is a finding.

ℹ️ Check

Note: If IPv6 is disabled on the system, this requirement is Not Applicable. Verify OL 8 does not accept router advertisements on all IPv6 interfaces, unless the system is a router. Determine if router advertisements are not accepted by using the following command: $ sysctl net.ipv6.conf.all.accept_ra net.ipv6.conf.all.accept_ra = 0 If the "accept_ra" value is not "0" and is not documented with the information system security officer (ISSO) as an operational requirement, this is a finding.

✔️ Fix
Configure OL 8 to not accept router advertisements on all IPv6 interfaces 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.ipv6.conf.all.accept_ra = 0 Load settings from all system configuration files with the following command: $ sudo sysctl --system