Information
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.
Solution
Step 1: Configure the ACL to deny packets with multicast administratively scoped destination addresses as shown in the example below:
SW2(config)#ip access-list standard MULTICAST_SCOPE
SW2(config-std-nacl)#deny 239.0.0.0 0.255.255.255
SW2(config-std-nacl)#permit any
SW2(config-std-nacl)#exit
Step 2: Apply the multicast boundary at the appropriate interfaces as shown in the example below:
SW2(config)#int g1/2
SW2(config-if)#ip multicast boundary MULTICAST_SCOPE
SW2(config-if)#end