Chapter 25: Multicast
STANDARD Revision 1.0 C4® CMTS Release 8.3 User Guide
© 2016 ARRIS Enterprises LLC. All Rights Reserved. 778
Note: The cable-mac must first be shut down for this change to complete.
Multicast Routing
Two forms of multicast are supported on the C4/c CMTS:
ASM — Any Source Multicast (ASM) denoted as (*,G)
ASM is a multicast control technique where clients join a selected multicast group (G) without specifying the source of
the multicast traffic.
SSM — Source-Specific Multicast (SSM) denoted as (S,G)
SSM clients join a selected multicast group and are also able to specify the source (S) from which to receive the
packets.
Valid Multicast Address Ranges
The following multicast addresses are supported by the C4/c CMTS:
SSM ranges 232.0.0.1 to 232.255.255.255 and 239.0.0.0 to 239.255.255.255
ASM ranges 224.0.1.0 to 231.255.255.255 and 239.0.0.0 to 239.255.255.255
Exceptions:
232.0.0.0 is reserved and should not be used. Join requests to this address will be dropped.
IGMP joins in the 224.0.0.0 - 224.0.0.255 range are reserved for the use of routing protocols (e.g. IGMP, OSPF) and
other low-level topology discovery or maintenance protocols and will be dropped.
IGMP joins in the 239.255.X.X range are defined as local non-routable and will be dropped. IGMP joins in this range can
be permitted through the use of an IGMP software ACL. (See IGMP ACLs (page 954)).
Note: By default, both ASM and SSM IGMP joins are permitted in the 239/8 range. ASM and SSM joins to the same
multicast group should be avoided since this will cause conflicts in the forwarding of multicast data traffic. ASM and SSM
conflicts in the 239/8 range can be avoided by defining multicast ranges in the QOS group. (See Configure QoS Groups
(page 760)).
For all other cases, an ASM join to an SSM group will be ignored and a SSM join to an ASM group will also be ignored.
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