Ip Igmp Snooping Source-Only-Learning Age-Timer - Cisco Catalyst 3550 Command Reference Manual

ip igmp snooping source-only-learning age-timer

ip igmp snooping source-only-learning age-timer
Use the ip igmp snooping source-only-learning age-timer global configuration command to enable
and configure the aging time of the forward-table entries that the switch learns by using the source-only
learning method. Use the no form of this command to return to the default setting.
Syntax Description
time
Defaults
The aging feature is enabled. The default is 600 seconds (10 minutes).
Command Modes Global configuration
Command History Release
12.1(14)EA1
Usage Guidelines
In a source-only network, switch ports are connected to multicast source ports and multicast router ports.
The switch ports are not connected to hosts that send IGMP join or leave messages.
The switch learns about IP multicast groups that alias with the reserved, destination, IP multicast
addresses (in the range 224.0.0.xxx) from the IP multicast data stream by using the source-only learning
method. The switch forwards traffic that aliases with these multicast addresses only to the multicast
router ports. You cannot disable IP multicast-source-only learning for traffic that aliases with these
multicast addresses.
The aging time only affects the forwarding-table entries that the switch learns by using the source-only
learning method. If the aging time is too long or is disabled, the forwarding table is filled with unused
multicast addresses that the switch learned by using source-only learning or by using the IGMP join
messages. When the switch receives traffic for new IP multicast groups, it floods the packet to all ports
in the same VLAN. This unnecessary flooding can impact switch performance.
To disable the aging of the forwarding-table entries, enter the ip igmp snooping source-only-learning
age-timer 0 global configuration command. If aging is disabled and you want to delete multicast
addresses that the switch learned by using source-only-learning, re-enable aging of the forwarding-table
entries. The switch can now age out the multicast addresses that were learned by the source-only learning
method and that are not in use.
Catalyst 3550 Multilayer Switch Command Reference
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ip igmp snooping source-only-learning age-timer time
no ip igmp snooping source-only-learning age-timer
Aging time is seconds. The range is 0 to 2880 seconds. If you set time to 0,
aging of the forward-table entries is disabled.
Modification
This command was introduced.
Chapter 2 Catalyst 3550 Switch Cisco IOS Commands
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