Configuration Guide User guide

1464 FastIron Configuration Guide
53-1002494-02
IGMP snooping overview
Support for IGMP snooping and Layer 3 multicast routing
together on the same device
The Brocade device supports global Layer 2 IP multicast traffic reduction (IGMP snooping) and
Layer 3 multicast routing (DVMRP or PIM-Sparse or PIM-Dense) together on the same device in the
full Layer 3 software image, as long as the Layer 2 feature configuration is at the VLAN level.
Refer to “IP multicast protocols and IGMP snooping on the same device” on page 1606.
Configuration notes and feature limitations
for IGMP snooping and Layer 3 multicast routing
The following details apply to FastIron X Series devices:
• Layer 2 IGMP snooping is automatically enabled with Layer 3 multicast routing. If Layer 3
multicast routing is enabled on your system, do not attempt to enable Layer 2 IGMP snooping.
• The default IGMP version is V2.
• A user can configure the maximum numbers of group address entries.
• An IGMP device can be configured to rate-limit the forwarding IGMP V2 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 these specific ports.
• If a VLAN has a connection to a PIM- or DVMRP-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 or DVMRP 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 hardware resource. Hardware resource is installed only when there is
data traffic. If 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. Brocade
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.
• FastIron X Series devices support VSRP together with IGMP snooping on the same interface.
• When VSRP or VSRP-aware is configured on a VLAN, the VLAN will support IGMP snooping
version 2 only. IGMP version 3 will not be supported on the VLAN.
• High CPU utilization occurs when IGMP Snooping and PIM or DVMRP routing are enabled
simultaneously on FastIron X Series devices. With IGMP snooping and PIM or DVMRP Routing
enabled simultaneously on a given system, IP Multicast data packets received in the snooping
VLAN(s) are forwarded to client ports via the hardware; however, copies of these packets will
also be received and dropped by the CPU.