Windows Server 2019 must be configured to prevent Internet Control Message Protocol (ICMP) redirects from overriding Open Shortest Path First (OSPF)-generated routes.

Allowing ICMP redirect of routes can lead to traffic not being routed properly. When disabled, this forces ICMP to be routed via the shortest path first.

If the following registry value does not exist or is not configured as specified, this is a finding:

Registry Hive: HKEY_LOCAL_MACHINE Registry Path: \SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\

Value Name: EnableICMPRedirect

Value Type: REG_DWORD Value: 0x00000000 (0)

Configure the policy value for Computer Configuration >> Administrative Templates >> MSS (Legacy) >> "MSS: (EnableICMPRedirect) Allow ICMP redirects to override OSPF generated routes" to "Disabled".

This policy setting requires the installation of the MSS-Legacy custom templates included with the STIG package. "MSS-Legacy.admx" and "MSS-Legacy.adml" must be copied to the \Windows\PolicyDefinitions and \Windows\PolicyDefinitions\en-US directories respectively.