The administrator must ensure that Protocol Independent Multicast (PIM) is disabled on all interfaces that are not required to support multicast routing.

From Perimeter Router Security Technical Implementation Guide

Part of PIM enabled on wrong interfaces

SV-40311r1_rule The administrator must ensure that Protocol Independent Multicast (PIM) is disabled on all interfaces that are not required to support multicast routing.

Vulnerability discussion

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.” Hence, it is imperative that the network has documented their multicast topology and thereby knows which interfaces are enabled for multicast. Once, this is done, the zones can be scoped as required.

Check content

If IPv4 or IPv6 multicast routing is enabled, ensure that all interfaces enabled for PIM is documented in the network’s multicast topology diagram. Review the router or multi-layer switch configuration to determine if multicast routing is enabled and what interfaces are enabled for PIM.

Fix text

If IPv4 or IPv6 multicast routing is enabled, ensure that all interfaces enabled for PIM is documented in the network’s multicast topology diagram. Enable PIM only on the applicable interfaces according to the multicast topology diagram.

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