IGMP snooping is supported on all 7210 SAS platforms as described in this document, including those configured in the access-uplink operating mode.
This section provides information about IGMP snooping support in a VPLS service. It does not apply to R-VPLS services. IGMP snooping can also be enabled for R-VPLS services. See R-VPLS and IGMPv3 snooping for more information.
In Layer 2 switches, multicast traffic is treated as an unknown MAC address or broadcast frame, which causes the incoming frame to be flooded out (broadcast) on every port within a VLAN. Although this is acceptable behavior for unknown and broadcast frames, this flooded multicast traffic may result in wasted bandwidth on network segments and end stations because IP multicast hosts can join and be interested in only specific multicast groups.
IGMP snooping uses information in Layer 3 protocol headers of multicast control messages to determine the processing at Layer 2. By doing so, an IGMP snooping switch provides the benefit of conserving bandwidth on those segments of the network in which no node has expressed interest in receiving packets addressed to the group address.
References to SDP in the following section about IGMP snooping are applicable only to 7210 SAS platforms operating in network mode.
IGMP snooping can be enabled in the context of VPLS services. The IGMP snooping optimizes the multicast data flow to only those SAPs or SDPs that are members of the group. The system builds a database of group members for each service by listening to IGMP queries and reports from each SAP or SDP, as follows:
When the switch receives an IGMP report from a host for a particular multicast group, the switch adds the host port number to the forwarding table entry.
When the switch receives an IGMP leave message from a host, it removes the host port from the table entry, if no other group members are present. It also deletes entries if it does not receive periodic IGMP membership reports from the multicast clients.
The following is a list of supported IGMP snooping features:
IGMPv1, IGMPv2, and IGMPv3 are supported in accordance with RFC 1112, Host Extensions for IP Multicasting, and RFC 2236, Internet Group Management Protocol, Version 2:
The 7210 SAS-T configured in the access-uplink operating mode supports IGMPv1, IGMPv2, and IGMPv3 snooping in a VPLS service.
All 7210 SAS platforms as described in this document, except those configured in the access-uplink operating mode, support only IGMPv1 and IGMPv2 snooping in a VPLS service.
IGMP snooping can be enabled and disabled on individual VPLS service instances.
IGMP snooping can be configured on individual SAPs that are part of a VPLS service. When IGMP snooping is enabled on a VPLS service, all its contained SAPs and SDPs automatically have snooping enabled.
Fast leave terminates the multicast session immediately, rather than using the standard group-specific query to check if other group members are present on the network.
SAPs and SDPs can be statically configured as multicast router ports. This allows the operator to control the set of ports to which IGMP membership reports are forwarded.
Static multicast group membership on a per-SAP and a per-SDP basis can be configured.
The maximum number of multicast groups (static and dynamic) that a SAP or SDP can join can be configured. An event is generated when the limit is reached.
The maximum number of multicast groups (static and dynamic) that a VPLS instance simultaneously supports can be configured.
Proxy summarization of IGMP messages reduces the number of IGMP messages processed by upstream devices in the network.
IGMP filtering allows a subscriber to a service or the provider to block, receive, or transmit permission (or both) to individual hosts or a range of hosts. The following types of filters can be defined:
Filter group membership that reports from a particular host or range of hosts. This filtering is performed by importing a defined routing policy into the SAP or SDP.
Filters that prevent a host from transmitting multicast streams into the network. The operator can define a data-plane filter (ACL) that drops all multicast traffic and apply this filter to a SAP or SDP.