The Cisco multicast edge router must be configured to establish boundaries for administratively scoped multicast traffic.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
low	V-216624	SRG-NET-000019-RTR-000005	CISC-RT-000810	SV-216624r531085_rule	2024-11-25	3

Description
If multicast traffic is forwarded beyond the intended boundary, it is possible that it can be intercepted by unauthorized or unintended personnel. Administrative scoped multicast addresses are locally assigned and are to be used exclusively by the enterprise network or enclave. Administrative scoped multicast traffic must not cross the enclave perimeter in either direction. Restricting multicast traffic makes it more difficult for a malicious user to access sensitive traffic. Admin-Local scope is encouraged for any multicast traffic within a network intended for network management, as well as for control plane traffic that must reach beyond link-local destinations.

Description

If multicast traffic is forwarded beyond the intended boundary, it is possible that it can be intercepted by unauthorized or unintended personnel. Administrative scoped multicast addresses are locally assigned and are to be used exclusively by the enterprise network or enclave. Administrative scoped multicast traffic must not cross the enclave perimeter in either direction. Restricting multicast traffic makes it more difficult for a malicious user to access sensitive traffic. Admin-Local scope is encouraged for any multicast traffic within a network intended for network management, as well as for control plane traffic that must reach beyond link-local destinations.

ℹ️ Check
Review the router configuration and verify that admin-scope multicast traffic is blocked at the external edge as shown in the example below. interface GigabitEthernet1/2 ip address x.1.12.2 255.255.255.252 ip pim sparse-mode ip multicast boundary MULTICAST_SCOPE … … … ip access-list standard MULTICAST_SCOPE deny 239.0.0.0 0.255.255.255 permit any If the router is not configured to establish boundaries for administratively scoped multicast traffic, this is a finding.

ℹ️ Check

Review the router configuration and verify that admin-scope multicast traffic is blocked at the external edge as shown in the example below. interface GigabitEthernet1/2 ip address x.1.12.2 255.255.255.252 ip pim sparse-mode ip multicast boundary MULTICAST_SCOPE … … … ip access-list standard MULTICAST_SCOPE deny 239.0.0.0 0.255.255.255 permit any If the router is not configured to establish boundaries for administratively scoped multicast traffic, this is a finding.

✔️ Fix
Step 1: Configure the ACL to deny packets with multicast administratively scoped destination addresses as shown in the example below. R2(config)#ip access-list standard MULTICAST_SCOPE R2(config-std-nacl)#deny 239.0.0.0 0.255.255.255 R2(config-std-nacl)#permit any R2(config-std-nacl)#exit Step 2: Apply the multicast boundary at the appropriate interfaces as shown in the example below. R2(config)#int g1/2 R2(config-if)#ip multicast boundary MULTICAST_SCOPE R2(config-if)#end

✔️ Fix

Step 1: Configure the ACL to deny packets with multicast administratively scoped destination addresses as shown in the example below. R2(config)#ip access-list standard MULTICAST_SCOPE R2(config-std-nacl)#deny 239.0.0.0 0.255.255.255 R2(config-std-nacl)#permit any R2(config-std-nacl)#exit Step 2: Apply the multicast boundary at the appropriate interfaces as shown in the example below. R2(config)#int g1/2 R2(config-if)#ip multicast boundary MULTICAST_SCOPE R2(config-if)#end