Internet Group Management Protocol (IGMP) | 217
Disabling Multicast Flooding
If the switch receives a multicast packet that has an IP address of a group it has not learned (unregistered
frame), the switch floods that packet out of all ports on the VLAN.
On the MXL Switch, when you configure
no ip igmp snooping flood, the system forwards the frames on
mrouter ports for first 96 IGMP snooping enabled VLANs. For all other VLANs, the unregistered
multicast packets are dropped.
Specifying a Port as Connected to a Multicast Router
To statically specify a port in a VLAN as connected to a multicast router, use the ip igmp snooping mrouter
command from INTERFACE VLAN mode.
To view the ports that are connected to multicast routers, use the
show ip igmp snooping mrouter command
from EXEC Privilege mode.
Configuring the Switch as Querier
Hosts that do not support unsolicited reporting wait for a general query before sending a membership
report. When the multicast source and receivers are in the same VLAN, multicast traffic is not routed, so
there is no querier. You must configure the switch to be the querier for a VLAN so that hosts send
membership reports and the switch can generate a forwarding table by snooping.
To configure the switch to be the querier for a VLAN, first assign an IP address to the VLAN interface,
and then use the
ip igmp snooping querier command from INTERFACE VLAN mode.
• IGMP snooping querier does not start if there is a statically configured multicast router interface in the
VLAN.
• 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, the 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.
To adjust the LMQI, use the
ip igmp snooping last-member-query-interval command from INTERFACE VLAN
mode.
To Next Page
Loading...
