The Cisco ACI layer 2 switch must have Internet Group Management Protocol (IGMP) or Multicast Listener Discovery (MLD) snooping configured on all VLANs.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
low	V-272039	SRG-NET-000512-L2S-000002	CACI-L2-000011	SV-272039r1168265_rule	2025-12-11	1

Description
IGMP and MLD snooping provides a way to constrain multicast traffic at layer 2. By monitoring the IGMP or MLD membership reports sent by hosts within a VLAN, the snooping application can set up Layer 2 multicast forwarding tables to deliver specific multicast traffic only to interfaces connected to hosts interested in receiving the traffic, thereby significantly reducing the volume of multicast traffic that would otherwise flood the VLAN.

Description

IGMP and MLD snooping provides a way to constrain multicast traffic at layer 2. By monitoring the IGMP or MLD membership reports sent by hosts within a VLAN, the snooping application can set up Layer 2 multicast forwarding tables to deliver specific multicast traffic only to interfaces connected to hosts interested in receiving the traffic, thereby significantly reducing the volume of multicast traffic that would otherwise flood the VLAN.

ℹ️ Check
Verify the switch configuration enables IGMP and MLD snooping for IPv4 and IPv6 multicast traffic. To show that the IGMP or MLD policy is assigned to the correct Bridge domain, navigate to Tenants >> {{Your_Tenant}} >> Networking >> Bridge Domains >> {{your_BridgeDomain}} >> Policy >> General. Select the IGMP snoop Policy and MLD Snoop Policy. If the switch is not configured to implement IGMP or MLD snooping for each bridge domain, this is a finding.

ℹ️ Check

Verify the switch configuration enables IGMP and MLD snooping for IPv4 and IPv6 multicast traffic. To show that the IGMP or MLD policy is assigned to the correct Bridge domain, navigate to Tenants >> {{Your_Tenant}} >> Networking >> Bridge Domains >> {{your_BridgeDomain}} >> Policy >> General. Select the IGMP snoop Policy and MLD Snoop Policy. If the switch is not configured to implement IGMP or MLD snooping for each bridge domain, this is a finding.

✔️ Fix
Configure IGMP and MLD snooping for IPv4 and IPv6 multicast traffic respectively globally. To show that the IGMP and/or MLD policy is assigned to the correct Bridge domain, navigate to Tenants >> {{Your_Tenant}} >> Networking >> Bridge Domains >> {{your_BridgeDomain}} >> Policy >> General. Select the IGMP snoop Policy and MLD Snoop Policy.