3.3.4 MLD Snooping ACL

Information

Multicast Listener Discovery (MLD) snooping is a feature designed to optimize multicast traffic across the network by preventing multicast flooding within a VLAN. MLD snooping forwards multicast traffic only to ports that have initiated an MLD request for the multicast group. Additionally, MLD snooping supports configuration to drop packets that do not match the configured version and allows blocking multicast traffic on specific ports. This mechanism reduces unnecessary multicast traffic and improves network efficiency.

Similar to IGMP, malicious users can generate invalid multicast entries using MLD reports, which can overwhelm the device and disrupt legitimate multicast services. To mitigate this risk, a multicast group policy configured with an ACL is used to filter MLD reports. The Layer 2 device adds a host's port to the outgoing port list only if the MLD report complies with the policy. This ensures that only authorized multicast group traffic is forwarded, providing enhanced security and avoiding unnecessary resource consumption.

Solution

To configure the MLD snooping ACL -

switch(config)# ipv6 mld snooping apply access list <ACL-NAME>

Impact:

When an ACL is applied to MLD snooping, only permitted group addresses in MLD packets are processed. The packets containing allowed group addresses are forwarded to the querier and PIM router, while the traffic for denied groups is blocked by the ACL.If all multicast groups in an MLD packet are denied by the ACL, the packet is not forwarded, and existing join messages for those groups will time out.Ports that do not match the MLD group policy are blocked from receiving multicast traffic, ensuring that unauthorized or excessive traffic does not propagate across the network.

See Also

https://workbench.cisecurity.org/benchmarks/24202

Item Details

Category: ACCESS CONTROL, SECURITY ASSESSMENT AND AUTHORIZATION, MEDIA PROTECTION, SYSTEM AND COMMUNICATIONS PROTECTION

References: 800-53|AC-3, 800-53|AC-5, 800-53|AC-6, 800-53|CA-7, 800-53|MP-2, 800-53|SC-4, CSCv7|14.6, CSCv7|14.7

Plugin: ArubaOS

Control ID: 6abfe5b86b44f5f011ed3ac120ac9551104dfe2dccc7122858c803b93a7a0f51