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Cisco 7600 Series Router Cisco IOS Software Configuration Guide, Release 12.2SX
OL-4266-08
Chapter 30 Configuring IGMP Snooping for IPv4 Multicast Traffic
IGMP Snooping Configuration Guidelines and Restrictions
IGMP Snooping Configuration Guidelines and Restrictions
When configuring IGMP snooping, follow these guidelines and restrictions:
•
To support Cisco Group Management Protocol (CGMP) client devices, configure the Multilayer
Switch Feature Card (MSFC) as a CGMP server. Refer to the
Cisco IOS IP and IP Routing
Configuration Guide
, Release 12.2, “IP Multicast,” “Configuring IP Multicast Routing,” at
this URL:
http://www.cisco.com/en/US/docs/ios/12_2/ip/configuration/guide/1cfmulti.html
•
For more information on IP multicast and IGMP, refer to RFC 1112 and RFC 2236.
•
IGMP snooping supports private VLANs. Private VLANs do not impose any restrictions on IGMP
snooping.
•
IGMP snooping constrains traffic in MAC multicast groups 0100.5e00.0001 to 0100.5eff.ffff.
•
IGMP snooping does not constrain Layer 2 multicasts generated by routing protocols.
IGMP Snooping Querier Configuration Guidelines and
Restrictions
When configuring the IGMP snooping querier, follow these guidelines and restrictions:
•
The IGMP snooping querier does not support querier elections. Enable the IGMP snooping querier
on only one router in the VLAN. (
CSCsk48795
)
•
Configure the VLAN in global configuration mode (see
Chapter 14, “Configuring VLANs”
).
•
Configure an IP address on the VLAN interface (see
Chapter 22, “Configuring Layer 3 Interfaces”
).
When enabled, the IGMP snooping querier uses the IP address as the query source address.
•
If there is no IP address configured on the VLAN interface, the IGMP snooping querier does not
start. The IGMP snooping querier disables itself if the IP address is cleared. When enabled, the
IGMP snooping querier restarts if you configure an IP address.
•
The IGMP snooping querier supports IGMP version 2.
•
When enabled, the IGMP snooping querier does not start if it detects IGMP traffic from a multicast
router.
•
When enabled, the IGMP snooping querier starts after 60 seconds with no IGMP traffic detected
from a multicast router.
•
When enabled, the IGMP snooping querier disables itself if it detects IGMP traffic from a multicast
router.
•
QoS does not support IGMP packets when IGMP snooping is enabled.
Note
When you are in configuration mode you can enter EXEC mode commands by entering the
do
keyword
before the
EXEC mode command.