Configuration Notes and Feature Limitations for IGMP Snooping and Layer 3 Multicast Routing
- IGMP snooping is supported for the default VLAN.
- Layer 2 IGMP multicast is automatically enabled with Layer 3 multicast routing. Layer 2 IGMP snooping and Layer 3 multicast routing cannot be configured on the same VLAN.
- The default IGMP version is IGMPv2.
- A user can configure the maximum number of group address entries.
- An IGMP device can be configured to rate limit the forwarding IGMPv2 membership reports to queriers.
- The device supports static groups. The device acts as a proxy to send IGMP reports for the static groups when receiving queries.
- A user can configure static router ports to force all multicast traffic to the specific static router ports.
- When there are two or more possible queriers, it is recommended to configure the IP multicast age interval to 20 seconds more than the default calculated age interval on all switches enabled with IGMP snooping. This prevents the aging of groups when the active querier fails.
- If a VLAN has a connection to a PIM-enabled port on another router, the VLAN must be configured as a non-querier (passive). When multiple snooping devices connect together and there is no connection to PIM ports, one device must be configured as a querier (active). If multiple devices are configured as active (queriers), only one will keep sending queries after exchanging queries.
- The querier must configure an IP address to send out queries.
- IGMP snooping requires a hardware resource. A hardware resource is installed only when there is data traffic. If the resource is inadequate, the data stream without a resource is mirrored to the CPU in addition to being VLAN flooded, which can cause high CPU usage. RUCKUS recommends that you avoid global enabling of snooping unless necessary.
- IGMP snooping requires clients to send membership reports in order to receive data traffic. If a client application does not send reports, you must configure static groups on the snooping VLAN to force traffic to client ports. Note that servers (traffic sources) are not required to send IGMP memberships.
- IGMP Snooping creates the mcache upon receipt
of multicast data traffic or membership reports:
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By default, for IGMP snooping running in IGMPv2 mode, the mcache (*,G) is created when data traffic is received, or upon receipt of IGMPv2 reports.
- By default, for IGMP snooping running in IGMPv3 mode, the mcache (S,G) is created when data traffic is received or upon receipt of IGMPv3 reports containing source information.
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- VSRP together with IGMP snooping is supported on the same interface.
- When VSRP or VSRP-aware is configured on a VLAN, only IGMPv2 is recommended; IGMPv3 is not recommended.
- Each VLAN can independently enable or disable IGMP, or configure IGMPv2 or IGMPv3.
- IGMP/PIM SM snooping over Multi-Chassis Trunking (MCT) is supported on the following RUCKUS ICX devices:
- IGMP snooping is IP-based for all RUCKUS ICX devices.
- Only one mcache will be created for all multicast groups that share same multicast MAC address. The mcache will be created for the group for which the packets first arrive.