Fast Convergence After Mstp Topology Changes; Designating A Multicast Router Interface - Dell Force10 S4810P Configuration Manual

High-density, 1ru 48-port 10gbe switch

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IGMP snooping Querier does not start if there is a statically configured multicast router interface in the

The switch may lose the querier election if it does not have the lowest IP address of all potential

queriers on the subnet.

When enabled, IGMP snooping Querier starts after one query interval in case no IGMP general query

(with IP SA lower than its VLAN IP address) is received on any of its VLAN members.

Adjusting the Last Member Query Interval

When the querier receives a leave message from a receiver, it sends a group-specific query out of the ports

specified in the forwarding table. If no response is received, it sends another. The amount of time that the

querier waits to receive a response to the initial query before sending a second one is the Last Member

Query Interval (LMQI). The switch waits one LMQI after the second query before removing the

group-port entry from the forwarding table.

Adjust the Last Member Query Interval using the command

from INTERFACE VLAN mode.

Fast Convergence after MSTP Topology Changes

When a port transitions to the Forwarding state as a result of an STP or MSTP topology change, FTOS

sends a general query out of all ports except the multicast router ports. The host sends a response to the

general query and the forwarding database is updated without having to wait for the query interval to

When an IGMP snooping switch is not acting as a Querier it sends out the general query , in response to the

MSTP triggered link-layer topology change, with the source IP address of 0.0.0.0 to avoid triggering

Querier election.

You can designate an interface as a multicast router interface with the command

. FTOS also has the capability of listening in on the incoming IGMP General Queries and

designate those interfaces as the multicast router interface when the frames have a non-zero IP source

address. All IGMP control packets and IP multicast data traffic originating from receivers is forwarded to

multicast router interfaces.

Internet Group Management Protocol (IGMP)

ip igmp snooping last-member-query-interval

ip igmp snooping mrouter