The administrator must ensure that boundaries are established at the enclave perimeter for all administrative scoped multicast traffic.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-30579	NET-MCAST-009	SV-40319r1_rule		Medium

Description
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.

Description

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.

STIG	Date
Perimeter Router Security Technical Implementation Guide Juniper	2018-11-28

Details

Check Text ( C-39200r1_chk )
An administratively scoped IP multicast region is defined to be a topological region in which there are one or more boundary routers with common boundary definitions. Such a router is said to be a boundary for multicast scoped addresses in the range defined in its configuration. In order to support administratively scoped multicast, a multicast boundary router will drop multicast traffic matching an interface's boundary definition in either direction. The IPv4 administrative scoped multicast address space is 239/8 which is divided into two scope levels: the Local Scope and Organization Local Scope. The 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 IPv4 Organization Local Scope is 239.192.0.0/14 is the space from which an organization should allocate sub-ranges when defining scopes for private use. This scope can be expanded to 239.128.0.0/10, 239.64.0.0/10, and 239.0.0.0/10 if necessary. The scope of IPv6 multicast packets are determined by the scope value where 4 (ffx4::/16) is Admin-local, 5 (ffx5::/16) is Site-local, and 8 (ffx8::/16) is Organization-local. The administratively scoped IPv4 multicast address space is 239.0.0.0 through 239.255.255.255. Packets addressed to administratively scoped multicast addresses must not cross administrative boundaries. You can configure multicast scoping with a scope statement or with a scope-policy statement as shown in the following examples: The following is an example using the scope statement to establish administrative scope boundary for both IPv4 and IPv6 multicast traffic: routing-options { multicast { scope ipv4-administrative-scope { interface [fe-1/1/1 fe-1/1/2]; prefix 239.0.0.0/8; } scope ipv6-administrative-scope { interface [fe-1/1/1 fe-1/1/2]; prefix FF08::/16; } } } Example using the scope-policy statement routing-options { multicast { scope-policy block-admin-scope; } } … … … policy-options { policy-statement block-admin-scope { term reject-i { from { route-filter 239.0.0.0/8 orlonger; route-filter FF08::/16 orlonger; } then reject; } } }

Check Text ( C-39200r1_chk )

An administratively scoped IP multicast region is defined to be a topological region in which there are one or more boundary routers with common boundary definitions. Such a router is said to be a boundary for multicast scoped addresses in the range defined in its configuration. In order to support administratively scoped multicast, a multicast boundary router will drop multicast traffic matching an interface's boundary definition in either direction.

The IPv4 administrative scoped multicast address space is 239/8 which is divided into two scope levels: the Local Scope and Organization Local Scope. The 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 IPv4 Organization Local Scope is 239.192.0.0/14 is the space from which an organization should allocate sub-ranges when defining scopes for private use. This scope can be expanded to 239.128.0.0/10, 239.64.0.0/10, and 239.0.0.0/10 if necessary. The scope of IPv6 multicast packets are determined by the scope value where 4 (ffx4::/16) is Admin-local, 5 (ffx5::/16) is Site-local, and 8 (ffx8::/16) is Organization-local.

The administratively scoped IPv4 multicast address space is 239.0.0.0 through 239.255.255.255. Packets addressed to administratively scoped multicast addresses must not cross administrative boundaries. You can configure multicast scoping with a scope statement or with a scope-policy statement as shown in the following examples:

The following is an example using the scope statement to establish administrative scope boundary for both IPv4 and IPv6 multicast traffic:

routing-options {
multicast {
scope ipv4-administrative-scope {
interface [fe-1/1/1 fe-1/1/2];
prefix 239.0.0.0/8;
}
scope ipv6-administrative-scope {
interface [fe-1/1/1 fe-1/1/2];
prefix FF08::/16;
}
}
}

Example using the scope-policy statement

routing-options {
multicast {
scope-policy block-admin-scope;
}
}
…
…
…
policy-options {
policy-statement block-admin-scope {
term reject-i {
from {
route-filter 239.0.0.0/8 orlonger;
route-filter FF08::/16 orlonger;
}
then reject;
}
}
}

Fix Text (F-34302r1_fix)
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 IPv4 Organization Local Scope is 239.192.0.0/14 is defined to be and is the space from which an organization should allocate sub- ranges when defining scopes for private use. The scope of IPv6 multicast packets are determined by the scope value where 4 is Admin-local, 5 is Site-local, and 8 is Organization-local. Configure the necessary boundary to ensure packets addressed to these administratively scoped multicast addresses do not cross the applicable administrative boundaries.

Fix Text (F-34302r1_fix)

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 IPv4 Organization Local Scope is 239.192.0.0/14 is defined to be and is the space from which an organization should allocate sub- ranges when defining scopes for private use. The scope of IPv6 multicast packets are determined by the scope value where 4 is Admin-local, 5 is Site-local, and 8 is Organization-local. Configure the necessary boundary to ensure packets addressed to these administratively scoped multicast addresses do not cross the applicable administrative boundaries.