PowerConnect B-Series FCX Configuration Guide 65153-1002266-01IGMP snooping overview 22The <num> value can be 4, 8, 16, or 32. Any other value is truncated to the closest lower ceiling.For example, a value of 15 is changed to 8. The default hash chain length is 4. A chain length ofmore than 4 may affect line rate switching.NOTEFor this command to take effect, you must save the configuration and reload the switch.The hardware resource limit applies only to the VLANs where IGMP snooping is enabled. Multicaststreams are switched in hardware without using any pre-installed resources in a VLAN wheresnooping is not enabled.PowerConnect B-Series FCX devices support up to 32K of IGMP groups, which are produced byclient membership reports.Configuration notes• Servers (traffic sources) are not required to send IGMP memberships.• The default IGMP version is V2.• Hardware resource is installed only when there is data traffic. If a VLAN is configured forIGMPv3, the hardware matches (S G), otherwise it matches (* G).• A user can configure the maximum numbers of groups and hardware switched data streams.• The device supports static groups that apply to the entire VLAN, or to just a few ports. Thedevice acts as a proxy to send IGMP reports for the static groups when receiving queries. Thestatic group has a drop option to discard multicast data packets in hardware.• A user can configure static router ports to force all multicast traffic to these specific ports.• The devices support fast leave for IGMPv2. Fast leave stops traffic immediately when the portreceives a leave message.• The devices support tracking and fast leave for IGMPv3, tracking all IGMPv3 clients. If the onlyclient on a port leaves, traffic is stopped immediately.• An IGMP device can be configured as a querier (active) or non-querier (passive). Queriers sendqueries. Non-queriers listen for queries and forward them to the entire VLAN.• Every VLAN can be independently configured to be a querier or a non-querier.• If a VLAN has a connection to a PIM or DVMRP-enabled port on another router, this VLAN mustbe configured as a non-querier (passive). When multiple snooping devices connect togetherand there is no connection to PIM or DVMRP ports, one device must be configured as a querier(active). If multiple devices are configured as active (queriers), only one will keep sendingqueries after exchanging queries.• An IGMP device can be configured to rate-limit the forwarding IGMPv2 membership reports toqueriers.• The querier must configure an IP address to send out queries.• When VSRP or VSRP-aware is configured on a VLAN, the VLAN will support IGMP snoopingversion 2 only. IGMP version 3 will not be supported on the VLAN.• When OSPF/PIM/VRRP is configured on a VLAN on the PowerConnect B-Series FCX , the VLANwill support IGMP snooping version 1 and version 2. IGMP snooping version 3 will not besupported on the VLAN.
