Chapter 25: Multicast
STANDARD Revision 1.0
C4® CMTS Release 8.3 User Guide
© 2016 ARRIS Enterprises LLC. All Rights Reserved.
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There is an implicit deny to any other multicast IP ranges.
The following command applies the ACL to the IGMP-configured interface:
configure interface cable-mac 1.0 ip igmp access-group 10
Source-specific modes for IGMP are not supported by the IGMP ACL feature. Support for filtering on both source address
and group address of IGMP join requests is planned for a future release.
A permit ACL entry means that the join is processed normally; a deny ACL entry means the join request is ignored. If the
specified access-group does not exist, then all IGMP joins are accepted. If an access-group is specified but the group
address does not match any entry in the ACL, then an implicit deny occurs and the join request is ignored.
Use
show ip igmp interfaces
to display the access-group assigned to an interface. If no access-group is assigned, then
the text Inbound IGMP access group is not set is displayed. If an access-group is assigned, then the text Inbound IGMP
access group is <acl-id> is displayed. The ACL feature supports both names and numbers.
Static IGMP Joins
IGMP memberships can be statically defined in two ways via either a static host join or a static router join. Both methods
are capable of static SSM or ASM joins. These were also known as static non-SSM joins. However, the static router join is
the preferred method.
Static host joins simply has the router itself join a group. The router will act as any other host in the network sending out
IGMP membership report messages for the membership. If the IGMP router functionality is turned on for the interface, it
sees these membership report messages thus learning about the need for a host on the network to receive traffic for the
joined multicast group. The command to do a host join is:
configure interface cable <slot/port> ip igmp join-group <group> [source <source>]
configure interface cable-mac <mac>.<subif> ip igmp join-group <group> [source <source>]
Static router joins differ from host joins because there is no IGMP messaging involved. If the IGMP router functionality is
enabled on the interface doing the static router join, the router both "learns" the membership and also filters out any
IGMP membership state received by the router via IGMP membership reports and leaves. No external event can remove
the membership.
Static router joins can be configured at different interface levels. The first is at the layer 3 interface level where the router