Dell S6000 FTOS 9.0(2.0) Configuration Guide for the System - Page 381

Configuring a Static IGMP Group, Enabling IGMP Immediate-leave, IGMP Snooping

Page 381 highlights

2. When a router receives a query, it compares the IP address of the interface on which it was received with the source IP address given in the query. If the receiving router IP address is greater than the source address given in the query, the router stops sending queries. By this method, the router with the lowest IP address on the subnet is elected querier and continues to send queries. 3. If a specified amount of time elapses during which other routers on the subnet do not receive a query, those routers assume that the querier is down, and a new querier is elected. The amount of time that elapses before routers on a subnet assume that the querier is down is the Other Querier Present Interval. Adjust this value using the ip igmp querier-timeout command from INTERFACE mode. Configuring a Static IGMP Group Configure a static IGMP group using the ip igmp static-group command. Multicast traffic for static groups is always forwarded to the subnet even if there are no members in the group. View the static groups using the show ip igmp groups command from EXEC Privilege mode. Static groups have an expiration value of Never and a Last Reporter value of CLI, as shown in Figure 19-8. Enabling IGMP Immediate-leave If the querier does not receive a response to a group-specific or group-and-source query, it sends another query (Querier Robustness Value). Then, after no response, the querier removes the group from the outgoing interface for the subnet. IGMP Immediate Leave reduces leave latency by enabling a router to immediately delete the group membership on an interface upon receiving a Leave message (it does not send any group-specific or group-and-source queries before deleting the entry). Configure the system for IGMP Immediate Leave using the ip igmp immediate-leave command. View the enable status of this feature using the show ip igmp interface command from EXEC Privilege mode, as shown in Figure 19-7. IGMP Snooping Multicast packets are addressed with multicast MAC addresses, which represent a group of devices, rather than one unique device. Switches forward multicast frames out of all ports in a virtual local area network (VLAN) by default, even though there may be only some interested hosts, which is a waste of bandwidth. IGMP Snooping enables switches to use information in IGMP packets to generate a forwarding table that associates ports with multicast groups so that when they receive multicast frames, they can forward them only to interested receivers. Internet Group Management Protocol (IGMP) | 359

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Internet Group Management Protocol (IGMP)
|
359
2.
When a router receives a query, it compares the IP address of the interface on which it was received
with the source IP address given in the query. If the receiving router IP address is greater than the
source address given in the query, the router stops sending queries. By this method, the router with the
lowest IP address on the subnet is elected querier and continues to send queries.
3.
If a specified amount of time elapses during which other routers on the subnet do not receive a query,
those routers assume that the querier is down, and a new querier is elected.
The amount of time that elapses before routers on a subnet assume that the querier is down is the Other
Querier Present Interval. Adjust this value using the
ip igmp querier-timeout
command
from INTERFACE
mode.
Configuring a Static IGMP Group
Configure a static IGMP group using the
ip igmp static-group
command. Multicast traffic for static groups
is always forwarded to the subnet even if there are no members in the group.
View the static groups using the
show ip igmp groups
command from EXEC Privilege mode. Static groups
have an expiration value of
Never
and
a Last Reporter value of
CLI
, as shown in
Figure 19-8
.
Enabling IGMP Immediate-leave
If the querier does not receive a response to a group-specific or group-and-source query, it sends another
query (Querier Robustness Value). Then, after no response, the querier removes the group from the
outgoing interface for the subnet.
IGMP Immediate Leave reduces leave latency by enabling a router to immediately delete the group
membership on an interface upon receiving a Leave message (it does not send any group-specific or
group-and-source queries before deleting the entry). Configure the system for IGMP Immediate Leave
using the
ip igmp immediate-leave
command.
View the enable status of this feature using the
show ip igmp interface
command from EXEC Privilege
mode, as shown in
Figure 19-7
.
IGMP Snooping
Multicast packets are addressed with multicast MAC addresses, which represent a group of devices, rather
than one unique device. Switches forward multicast frames out of all ports in a virtual local area network
(VLAN) by default, even though there may be only some interested hosts, which is a waste of bandwidth.
IGMP Snooping enables switches to use information in IGMP packets to generate a forwarding table that
associates ports with multicast groups so that when they receive multicast frames, they can forward them
only to interested receivers.