Multimedia Traffic Control with IP Multicast (IGMP)
Excluding Multicast Addresses from IP Multicast Filtering
Excluding Multicast Addresses from IP
Multicast Filtering
Each multicast host group is identified by a single IP address in the range of
224.0.0.0 through 239.255.255.255. Specific groups of consecutive addresses
in this range are termed “well-known” addresses and are reserved for
predefined host groups. IGMP does not filter these addresses, so any packets
the switch receives for such addresses are flooded out all ports assigned to
the VLAN on which they were received (except the port on which the packets
entered the VLAN).
The following table lists the 32 well-known address groups (8192 total
addresses) that IGMP does not filter on the switches covered in this guide, as
well as on the 1600M, 2400M, 2424M, 2650M, 4000M, 6108M, 8000M, and Switch
2500 Series devices.
4-3.IP Multicast Address Groups Excluded from IGMP Filtering
Groups of Consecutive Addresses in
the Range of 224.0.0.X to 239.0.0.X*
Groups of Consecutive Addresses in
the Range of 224.128.0.X to 239.128.0.X*
224.0.0.x 232.0.0.x 224.128.0.x 232.128.0.x
225.0.0.x 233.0.0.x 225.128.0.x 233.128.0.x
226.0.0.x 234.0.0.x 226.128.0.x 234.128.0.x
227.0.0.x 235.0.0.x 227.128.0.x 235.128.0.x
228.0.0.x 236.0.0.x 228.128.0.x 236.128.0.x
229.0.0.x 237.0.0.x 229.128.0.x 237.128.0.x
230.0.0.x 238.0.0.x 230.128.0.x 238.128.0.x
231.0.0.x 239.0.0.x 231.128.0.x 239.128.0.x
* X is any value from 0 to 255.
Notes Reserved Addresses Excluded from IP Multicast (IGMP) Filtering.
Traffic to IP multicast groups in the IP address range of 224.0.0.0 to 224.0.0.255
will always be flooded because addresses in this range are “well known” or
“reserved” addresses. Thus, if IP Multicast is enabled and there is an IP
multicast group within the reserved address range, traffic to that group will
be flooded instead of filtered by the switch.
4-23
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