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Catalyst 4500 Series, Catalyst 2948G, Catalyst 2948G-GE-TX, and Catalyst 2980G Switches Software Configuration Guide—Release 8.2GLX
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Chapter 15 Configuring Multicast Services
Filtering IGMP Traffic
If a port is set to deny, matched IPs are dropped; all others are forwarded. If the filtering action causes
an IGMP packet to be dropped, the switch port requesting the stream of IP multicast traffic cannot
receive IP multicast traffic for that group.
Note IGMP filtering actions do not direct IP multicast traffic forwarding. For example, IGMP filtering does
not know if CGMP is used to allow IP multicast traffic forwarding.
The following sections describe IGMP traffic filtering usage, requirements, and configurations.
Using IGMP Traffic Filtering
You can use IGMP filters in video service deployment of Ethernet to the Home (ETTH).
IGMP transmits video channels as IP multicast traffic using MPEG encoding. In access switches, filters
specify which video channels (multicast addresses) are allowed to be received by every customer.
In ETTH, a typical access switch has two high-speed uplink ports. The other ports are user ports, each
connected to a different end subscriber who has a box that generates IGMP report and leave messages.
You can define which channels (IP multicast addresses) to monitor and the minimum monitoring
interval. If an end subscriber is looking at a channel for more than the minimum monitoring interval, an
entry is created in a monitoring table. IGMP monitoring creates statistics about channel changing
patterns of which channels are viewed when and for how long.
IGMP Software Requirements
IGMP requires software release 7.1(1) or later releases and has the following physical restrictions for
filtering through software:
• A threshold of 1024 profiles available on the Catalyst 4500 series switch
• A limit of 512 Class D multicast IP addresses that can be filtered in all profiles
• One (1) profile per port
Default IGMP Filter Configuration
Table 15-3 shows the default IGMP traffic filter configuration.
Table 15-3 IGMP Default Configuration
Feature Default Value
IGMP filtering None
IGMP enable state Disabled
IGMP match-action state Deny
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