OL 9 must not accept router advertisements on all IPv6 interfaces by default.

An illicit router advertisement message could result in a man-in-the-middle attack.

Note: If IPv6 is disabled on the system, this requirement is Not Applicable. Verify that OL 9 does not accept router advertisements on all IPv6 interfaces by default unless the system is a router. Determine if router advertisements are not accepted by default by using the following command: $ sysctl net.ipv6.conf.default.accept_ra net.ipv6.conf.default.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.

Configure OL 9 to not accept router advertisements on all IPv6 interfaces by default 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.default.accept_ra = 0 Load settings from all system configuration files with the following command: $ sudo sysctl --system