Excluding multicast addresses from IP multicast filtering
Each multicast host group is identified by a single IP address in the range 224.0.0.0 through 239.255.255.255. Specific groups of consecutive addresses in this range are “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 manual and on 1600M, 2400M, 2424M, 2650M, 4000M, 6108M, 8000M and switch 2500 series devices.
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[a] | Groups of consecutive addresses in the range of 224.128.0.x to 239.128.0.x[a] | ||
|---|---|---|---|
| 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 |
[a] x is any value from 0 to 255. | |||
![[NOTE: ]](images/note.gif) | NOTE: IP multicast filters. This operation applies to Switches 1600M, 2400M, 2424M, 4000M and 8000M, but not to Switches 2500, 2600, 2600PWR, 2800, 2810, 2510, 4100 and 5300 Series devices or Switch 6108, which do not have static multicast traffic/security filters). IP multicast addresses occur in the range 224.0.0.0 through 239.255.255.255 (corresponding to the Ethernet multicast address range 01005e-000000 through 01005e-7fffff). Where a switch has a static Traffic/Security filter configured with a “Multicast” filter type and a “Multicast Address” in this range, the switch uses the static filter unless IGMP learns of a multicast group destination in this range. In this case, IGMP dynamically takes over the filtering function for the multicast destination addresses) for as long as the IGMP group is active. If the IGMP group subsequently deactivates, the switch returns filtering control to the static filter. Reserved addresses excluded from IP multicast (IGMP) filtering. Traffic to IP multicast groups in the IP address range 224.0.0.0 to 224.0.0.255 are always 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 is flooded, not filtered, by the switch. Number of IP multicast addresses allowed. Multicast filters and IGMP filters (addresses) together can total up to 255 in the switch. If multiple VLANs are configured, then each filter is counted once per VLAN in which it is used. |