NET-MCAST-010 - No Admin-local or Site-local boundary - ip access-list standard - 'deny 239'

Information

The administrator must ensure that multicast routers are configured to establish boundaries for Admin-local or Site-local scope multicast traffic.

A scope zone is an instance of a connected region of a given scope. Zones of the same scope cannot overlap while zones of a smaller scope will fit completely within a zone of a larger scope. For example, Admin-local scope is smaller than Site-local scope, so the administratively configured boundary fits within the bounds of a site. According to RFC 4007 IPv6 Scoped Address Architecture (section 5), scope zones are also required to be 'convex from a routing perspective'-that is, packets routed within a zone must not pass through any links that are outside of the zone. This requirement forces each zone to be one contiguous island rather than a series of separate islands. As stated in the DoD IPv6 IA Guidance for MO3, 'One should be able to identify all interfaces of a zone by drawing a closed loop on their network diagram, engulfing some routers and passing through some routers to include only some of their interfaces.

Administrative scoped multicast addresses are locally assigned and are to be used exclusively by the enterprise network or enclave. Hence, administrative scoped multicast traffic must not cross the perimeter of the enclave in either direction. Admin-local scope could be used to contain multicast traffic to a portion of an enclave or within a site. This can make it more difficult for a malicious user to access sensitive traffic if the traffic is restricted to links that the user does not have access to. Admin-local scope is encouraged for any multicast traffic within a network that is intended for network management as well as control plane traffic that must reach beyond link-local destinations.

NOTE: Change 'MCAST_ADMIN_SCOPED_BOUNDARY' to the filter used to effect multicast traffic outside of the administratively scoped IPv4 multicast space.

Solution

Local Scope range is 239.255.0.0/16 and can expand into the reserved ranges 239.254.0.0/16 and 239.253.0.0/16 if 239.255.0.0/16 is exhausted. The scope of IPv6 multicast packets are determined by the scope value where 4 is Admin-local and 5 is Site-local. Configure the necessary boundary to ensure packets addressed to these administratively scoped multicast addresses do not cross the applicable administrative boundaries.

Item Details

Audit Name: DISA STIG Cisco Perimeter L3 Switch v8r32

Category: SYSTEM AND COMMUNICATIONS PROTECTION

Plugin: Cisco

Control ID: 83539ddd3fa31712f9fee6ba7b3bfbd0ec7472cd3fbabe7d792d8579f8fd1a4c

Detections

Analytics

NET-MCAST-010 - No Admin-local or Site-local boundary - ip access-list standard - 'deny 239'

Information

Solution

See Also

Item Details